+1 on Bill's report, very happy user here as well, since July 08, using Zeiss 24-70 f2.8, 135 F1.8, Sony 70-400G and 16mm fisheye. On the latter, the lense cap is a pest, made from leather and really not useful!
Yeah, a new TC that works with autofocus on the 70-400 would be great in deed. As for the 70-400, I also was more than surprised on the sharpness of this somewhat ugly finished lense. Then again, there are rather expensive camouflage covers on the market to deal with that silver finish.
Funny how you mentioned the thing with the red dot when changing lenses, it was always bugging me like crazy.
My biggest concern when buying into this system was on reliability, but luckily, I also have zero complaints in this department.
Looking forward to a next generation model in 2010, could be an interesting step up or not, remains to be seen. I for one, have zero interest in build in video applications. A few more Zeiss or G grade lenses would be nice as well.