Haha giving tours of Northeastern cities isnt my specialty but buses to get around (Especially Philly to NYC) sure is!!!!
Philly is a great city but you really need a good tour guide to get the most out of it. (There are all kinds of tours here including the bus tours that someone mentioned NYC having). Great city if your into lots of history and Philly is a city that I think everyone needs to visit once. Why I say you need a good tour guide is because even some of the areas in Center City can get kind of grimy and leave you with a bad impression of an otherwise great city (Just dont go to North Philly unarmed though, haha). For a first time visitor I would say also to make sure you wander down to South Street.
Boston I think you may just need to visit a couple times before you appreciate it. Ive been there I think 3 times and just like PosterFZ6,the first time I didnt really like it. The second time it was eh, not too bad and then the third time I enjoyed myself. I can see going a forth time and having a blast haha. Ive been meaning to go visit again and would like to in the near future.
DC like Boston I think Ive been to somewhere around 3 times. Great museums and cleaner subway system aside, I never really liked DC for some reason. Ive never been into touristy stuff so maybe your opinion will be vastly different than mine. Maybe I just dont like it because I never got a good local tour guide though

That after all is the biggest reason I can see someone not liking Philly.
I go back and forth on the buses all the time (Trying not to pile too much mileage onto my bike and now with winter upon us its getting too cold for the 1.5 to 2 hour ride) since I live in Philly but work in NYC.
Amtrak is way over priced. If money is no option its the fastest option and I always did have a thing for trains. There also is the option of combining the local trains from NJ Transit and Septa but it takes twice as long as Amtrak and still takes quite a bit longer than just taking the bus. Plus pricewise its still probably at least twice as much money as taking a bus. This is how I used to go back and forth many years ago before I knew about the Chinatown bus.
Many Chinatown buses have been shut down. The one from NYC to Boston I think is still running (Fung Wah) but I still cant find a Chinatown bus going from Center City Philly to NYC (there is one that will go from North East Philly but that is quite a ways out of the way) Usually the buses that went down to DC also stopped at Philly so I THINK its the same bus and shutdown but since I never go to DC there could be other companies that do it. Personally I think Chinatown buses have a reputation worse than they are, or maybe Im just used to them. Personally I still think their customer service is better than Greyhound, god I hate Greyhound... At least with the Chinatown buses you know that your bus may smell, that people will rush and bunch up trying to get on the bus before seats fill up, and the people running it dont speak perfect English. After commuting back and forth for a few years Ive never had a problem with the Chinatown bus other than a delay here and there. Ive had more delays with Greyhound and Ive been on WAY more Chinatown buses than Greyhound ones. I REALLY miss the Philly to NYC Chinatown bus. They always had another bus leaving every half hour to hour tops.
Even if you buy the ticket in person (for most Chinatown buses I would recommend it) a good site for seeing if there is a chinatown bus where you want to go is
http://www.gotobus.com
Other bus options:
Greyhound: Like I mentioned I hate Greyhound with a passion. Maybe I just expect more out such a big company and am harder on them then the Chinatown little guys but everyone that works there is always so miserable and it shows terribly in their customer service. Sure for a one time deal everything may work out ok but they have screwed me over way too many times. Only bonus to Greyhound is you have a nice warm (although the one in Philly is a bit smelly sometimes) station to wait for your bus in compared to the curbside buses. My personal thing with Greyhound is to only take them when there is no other option (Greyhound runs some late night buses for example and obviously goes more places). In recent years they have been
slowly getting nicer buses which are mostly used as express buses for the bigger cities. See:
Greyhound Express
Also note, Greyhound has started another bus line that is made to look like a Chinatown bus called "Yo Bus!" that goes from Philly to NYC Chinatown area. I dont have too much info about them and havent taken them yet. Supposedly they leave from the Greyhound terminal in Philly (which neighbors Chinatown) but I dont see too many of their buses when Im forced to take a Greyhound bus. As Chinatown is close to where I work in NYC I need to look into them soon.
Curbside buses: Both of the next two buses have prices that change depending on how busy that bus is. The earlier you buy your ticket the cheaper it will be. Its possible to get a $1 ticket if you book super early but people buy those seats up right away. No printout necessary just show them the code given to you when you buy your ticket, most people just show their phone.
Boltbus I havent taken for quite a while because they drop off at 30th st station and thats on the other side of the city from where I live. From what I remember they were always nice buses and on time and such. Even though they seem better managed they are still owned by Greyhound...
Now the best for last and my personal favorite Megabus for anywhere that they travel (Check out their site Megabus.com as they aways seem to slowly add more and more cities to the list). Coach USA is their parent company and is a very large bus company that also own alot of the tour buses in Philly. Their drivers always seem to be in a better mood then the Greyhound drivers and the buses always seem to be very clean. Double decker buses seem to be very rare in the US but Megabus has lots of them. Philly to NYC is a very busy route so they almost always use a double decker bus. The one time I took them to Boston from NYC it was a double decker too. I thought that was cool the first time I was on it. The bottom of the bus seems to be a
slightly nicer ride though and your less likely to bump your head. I also find the Megabus the easiest of the buses to fall sleep on. Im actually not really sure why but I almost always seem to fall asleep every time I take them, even when I dont mean to.
Oh and as for Revzilla in South Philly: I love them and think they are awesome, always super nice and always try their best to help. Ive dealt with just about every person that works in their showroom as I always buy from Revzilla before anyone else. I just wish they had more stuff on the showroom floor because half the things I want to look at are in the back. I recently found out that the main reason that they even have a showroom at all is because a lot of the brands they stock require a physical location you can visit (to prevent just anyone in their basement from selling things?). The positive of this is that the owner focuses mainly on the website sales and the people working in the showroom genuinely seem to like their jobs and are not trying to fill a sales quota while pressuring you to buy stuff NOW (and you dont feel bad for wasting their time just asking questions and buying on the site later when you have the money as I sometimes do). Unless you have a car or motorcycle they are a bit out of the way however. First time I went I had a little trouble finding them because they are on an industrialish back ally. I think, as someone who knows that area, it was just because I didnt expect to find any showrooms or stores on that street.