Just to balance the argument in this thread, as there are already many posts about plugging tires...
Generally if you are in the US it is frowned upon and if you are in Europe it's common place. I guess tires must be cheaper in the US.
The European opinion...
There is nothing wrong with plugging tires as long as it's a hole not a slash and it's at least 1 inch away from the side wall.
I've normally have to plug a few times a year (I commute to work on the bike) I would not have been able to replace the tires 3 times a year.
I've had a road-side repair pop out on me and nothing bad is going to happen, the tire does not disintegrate, it goes down at a slow rate, you feel it in the handling straight away and you have plenty of time to pull over to the side and sort it out.
I carry a kit very similar to
this, it has everything you need for a quick safe repair at the road side. Then once I'm back home I'll take the bike to the shop where they will take the tire off the wheel and do a plug from the inside of the tire which is impossible to force out at high speed.