Funny how similar we are sometimes. I also sold my 7D (still working on selling my 10-22) to help fund a 5DIII. I had a very early 7D, and was always disappointing in low light perf. I'd almost never go above 1600, 3200 only in emergency. The 5DIII has preposterously better IQ. It is so much better it feels like I'm cheating. Now when people complement my pictures by saying "you must have a great camera", I might not get mad, I might agree!
Yep, I lose a little reach. Fine-I'll crop or rent a lens when I need more than my 70-200mm f4L provides.
Besides IQ and AF, I like this about the 5D.
For me, handling and "feel" are very, very similar to 7D.
Menus are easier to get around.
DOF preview button is better now, although I've accidentally bumped it a few times,
Don't like as much:
Moved playback zoom button. Still keep messing that up...
Mode dial lock. Blech. The very few times I ever accidentally moved it, I just move it back. Over all much less effort then having to press the lock release button to turn it, esp if I am also holding a remote shutter release, my hat, glasses, lens cap, etc...
These are just niggles. Otherwise, this things is a monster.
So yes. WORTH IT.
That zoom feature drives me nuts! And I can't use the set button to zoom because I use it as my ISO button. (A great feature in my D30 as well.)