I'm a D5D user and I try A-100 in camera shop only. The first impression is that A-100 is generally better than or similiar to D5D. To me, I rank D5D with 9 marks. Thus, I mark A-100 with more than 9 marks.
The most userfriendly control button among the 1000 m.p. camera. The one touch/press button made you control some common function directly without entering the menu. It is hard to find such design in other high grade brand camera.
The lens of Tamron, Sigma and Tokina etc are available for the camera. There are very wide range/model with a reasonable price for your choice.
Sony is a very RICH company to provide a very good camera/movie camcoder deverlopment in the future.