Yes, the Sony lens selection is certainly narrower. I suppose it depends on what you use / need. For me 50/1.4, 24-70/2.8 and 70-200/2.8 is pretty much what I require, and Sony have fantastic examples of all three: all of them with IS, of course. But Canon has great lenses in these ranges, albeit without IS on the 24-70, as well as many other lenses I may want if my needs change.
The big news is the price. It's a great deal at $2k.
One seemingly small thing: the A900 did not have permanent display of ISO in the viewfinder, and I can't see that the 850 does either. This is the one thing that really bugs me on my 5D, which of course is 'fixed' on the Mk2.