I'd presume the format conflicts between M$ and Sony would complicate the issue ( BR-ROM being Sony's format )
But with all the extra storage there are plenty of possibilities for bonus content, such as development footage or documentaries, interviews with Crytek staff, and all the other extras you see on an average DVD. Deleted scenes, storyboards, music, artwork etc. You can do a lot with 25GB. And a quick install too!
Personally I think it could be a good idea, especially if they are the first developer to release a PC game on a BD.
I don't think anyone else has. Could be groundbreaking...