Thanks Richard, despite the quirks, we're super happy with the images we're getting. The low noise of ISO 1600 is incredible, compared to the 7D.

I'd wholly recommend full frame, but I wouldn't recommend going as far back as the 1Ds2 without knowing what you're getting yourself into. To change half the settings you need deprecated software on an XP machine with firewire. If you want to use EOS Utility, you'll need to find an older version, as they dropped support years ago. The controls really are super clunky, and the small low-res LCD isn't particularly good. As someone pointed out in either the "fullframe fever" thread, or the 6D thread, Canon is dropping support in a couple months, so there will be no replacement parts in case of failure.

In a couple months you can get a brand new shiny 6D, warrantied, likely amazing high-ISO, hopefully good servo. I imagine you'll find sales for $1800 pretty quick, just as we're seeing sales on the 5Dmk3. So, for the extra couple hundred, it would probably be worthwhile picking up the 6D, unless you need the weather sealing, integrated grip, the battery that lasts forever, pro level features. I'd bet the majority of users would prefer the UI, and IQ, and software improvements over the pro-level body.

The good thing is, if I have convinced anyone to go fullframe, I've timed it quite well, with Canon making it more affordable than ever, and I've done it early enough for you to save up your pennies. All you've got to do is wait patiently.