Back up for 5D.

Being unconvinced by Canon's crop cameras - I've cancelled two orders within the last two years - but needing an occasional digital backup for professional work, a colleague suggested just getting a 40D with a grip for the time being, with the added advantage it can just sit on the telephoto lens as a permanently ready, dust-free all in one long lens solution.

A nearly mint one is virtually free (at least in digi camera terms) these days, and can be sold off for a loss of about 50 quid, plus I can use it for dodgy remote work, or bung a cheap flexi UW housing on it without too much concern if it gets knackered. At 1.6x crop, it's still better than a 5D 2 or 3, in resolution, and it's reasonably well made.

I'm convinced re IQ for editorial work, but not so sure about AF tracking and how well it handles auto ISO. I can live without the latter, and I assume that with all cross sensors, the tracking will be good enough for someone with my skill level. Is there any reason not to go down this route, at least until Canon produces a camera I want to commit proper funds to?

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Adam