I've noticed that sites of Vimeo are now becoming increasingly more populated by videos shot on the 7d or 5dmk2 which show great quality and dof. As such, I was wondering what the main advantages to having a large bulky camera and heavy of adaptor still are over such a small camera (other than time you can record on the 7d/5d)?

You've stated what the negatives are with using an adaptor. The positives are that all your normal work flows are the same.

1) XLR audio inputs, level metering, etc...
2) A proper viewfinder.
3) File format options are much better (easier workflow)
4) Having the option of removing the adaptor for a standard wide depth of field video camera look (good for shooting sports, documenting something, etc....)
5) That's all I could think of off the top of my head :)

Don't get me wrong, the lines are very blurred right now. I'm just hoping that either Canon, Sony or ?? come out with a true camera that does it all. Maybe the Scarlet will be that camera? Dunno.....

And live HD monitoring via SDI or component! I'm presently enamored with my GH1, but being limited to the 3" LCD is a deal breaker for many situations.