Do you work first development on 3.0
Right now, we work on 2.x first, then port it to 3.0. However, this will most likely change in the very near future as Eclipse 3.0 gets closer to GA.
how much users work with eclipse 2 yet
Right now we still have a few percentage more on 2.x than 3.0, but expect that to continue to shift toward 3.0 as time moves forward.