I've actually messed around with a Sony 850 while Sony was doing some sort of promotion at their shop in NYC. While the body seems really wacky with all the buttons, with the grip attached, the buttons and wheels are basically in the same position no matter the orientation. The grip duplicates the buttons on the body in portrait orientation. Redundant, yes, but also strangely convenient.
The pro lenses seemed very nice. But their AF seemed noticeably slower. At least, I would point the camera and expect AF to lock in, but there was a heartbeat's tick before it did. And I could find things to make it hunt. As mentioned above, the pro lenses are expensive compared to Canon but perhaps about the same or a bit less than the pro lenses from Olympus. However, they have a lot of affordable level lenses, including the all the Minolta AF lenses of yore.
One caveat: My father has a Sony Alpha body - one of the low to mid range bodies. A couple of the Sony-brand lenses (an 18-200 and a 70-300) wouldn't connect properly with his camera body. The camera didn't recognize that a lens was mounted, or if it did, nearly immediately lost contact. Ironically, every Minolta lens has worked perfectly.
But Canon is now selling the Canon 5D mkII for $2499. 3200ISO looks like 400ISO on other cameras. Yeah, there is noise in the shadows, but the rest of the image is clean. And with a 17-40mm f4.0L lens, I am barely above $3000 in initial cost. Seemed a no brainer to me, but then I just might not have a brain. 😱