I started 2 years ago when I was on vacation on summer, so I did not have to do the big switch when I had a lot of work to do. It took me about 2 months to start to be any good, and a bit longer to overtake my qwerty speed.
I always have a laptop on me, so school computers are not really an issue. But I have done a lot of work on the linux computers at my school and I use qwerty there.

The pros:
- my wrists don't hurt anymore.
- I can type without looking
- I can type faster than I could in qwerty (about 110WPM)
Cons:
- somewhat of a PITA on other computers, but after I became pretty good at dvorak I slowly relearned qwerty, and now I can type qwerty at about 60WPM.
- You have to have an easy way to switch your computer if you want other people to use it. Although thats not really a problem on my iBook or my linux laptop.

Overall I though there would be more inconvenience to the switch. It has been really smooth and the combination of dvorak and my ergonomic keyboard my wrists are better. And since I am 17 saving my wrists is a good thing smile