Not to get personal, but say you get a 20d now: does your wife understand the need for a used 50d (or 7d, or ...) next [whenever]? I still love my 20d, but am wondering if you'll feel like you had enough of an upgrade.
You'll gain the ergonomics, 1/250 flash sync (vs. 1/200), etc.
You'll lose IR wireless remote, dust removal.
Which probably means it comes down to the ergo - just like most here have said.
Grip: I really wish I would have gotten one. I keep planning to upgrade; so I keep planning a grip for my NEXT camera. But the 20d just keeps treating me well...
So: Is this the camera you want to have for the length of time you'll likely keep it? If so, you'll likely be happy.