I didn't get much time to mess with the M2s I got in today as they were all reserved by customers and had to ship out, but initial impressions were:

1. the 100ED is huge.
2. they are all surprisingly light - full shipping weight of the 100ED with the camera adapter is about 9lbs.

I did pull an 80ED from its box and checked it out for a few minutes. I don't have an F-ED to compare side by side, but I was impressed with the optical quality.