A lot of Slumdog was shot with the SI-2K, probably no other camera could captured the footage, it really was the ultimate guerilla shoot.
Two issues with the 5D, skew and audio. We now have a box from Beachtek that fixes the audio issue, The Foundry have a plugin for AE and Nuke that'll fix the skew. I've had a very quick play with the 5D and a nice set of lenses, not much change out of $20K for the package though. Also keep in mind that you're stuck at 30fps.
For less than half that the EX1/3 is very hard to beat. There's a great post on DVInfo from a chap who could have taken anything but just went back to his naked EX. As he said it's just nice to pull a camera out of a bag and shoot.
The 5D mk II is not for everyone. For the people it was designed for it is truly amazing. Full frame sensor and high quality glass lends to a very true cinematic feel with the total control of the DoF.
The same qualities that make it great for situations where all the elements are in your control make it horrible for taking video of the dog running around the back yard or the kid playing baseball.
Editing is another issue .mov h.264 files are a pain on all but the highest end systems or a Mac.
I've had my 5d since December and love it. I already had a good set of Canon glass so $2500 was the outlay. You will want to add maybe a grand in accessories to lock down better audio, some support and a matte. If you don't have existing glass add on another $1500-2500.