I was at a conference all this week and took my G1 + kit and a couple of legacy lenses along with me to take images. I thought I might share some of the experiences with other users here.
My legacy lenses were a Oly OM 100 f2.8 and a Canon FD 300 f4 (I was hoping for a 200mm f4 but it didn't get here in time so it was only the 300)
From 7 or 8 rows back I was able to get images like this:
with the 300 but needed quite high ISO (1600) in the typically dimmer light of conferences. If you don't like flash in this environment (I don't, and the ceiling was quite high for using bounce well) then it really shows the advantages to be had with cameras with much better high iso performance.
I used a small monopod and balanced off the chair between my legs to reduce camera shake.
The 100 proved nice and the f2.8 was an advantage in getting that little less shake or subject blur from animated movement.
But even the Kit lens was useful, especially with its stabilisation I could get sharp images in positions where I was holding the camera overhead ....
some folks there had 40D's and 5DmkII cameras which honestly felt and looked like obtrusive bricks after getting used to the G1.
People did not react nearly as much to my pulling out the G1 an using it from the hip (looking down at screen) as happened when people pulled out their black bricks.
If I was a working professional however I'd perhaps want to have the higher ISO of cameras like the 5DMkII or D700