I have been using a 60D for about a half a year now as a backup camera to my 1Ds MkIII, so it's inevitable I have to compare them, and in many respects I love the 60D for what it offers. I did an entire assignment today with it, and the 1Ds acting as the backup, and it went off without a hitch! Why would I do that? The image quality was plenty good enough for the clients needs (event photography that will never print bigger than 12x18 max) and the flip out screen allowed me to effortlessly shoot over the heads of crowds,etc.
Sure, the autofocus is far less sophisticated, the files are a bit smaller, and it'll likely break if I ever drop it or drown it, but I kind of like not having an 8 lb. brick hanging off my neck, and the quality of the photos are quite remarkable in comparison to a camera that is almost 8 times more costly! I have used it for a shot or two in highly-controlled, high quality architectural work that printed at very large size and no one has ever pointed out any lack in these images amongst the ones shot with the flagship 1DsMIII! I'd be extremely hard pressed to notice the slight differences, found primarily in noise levels in deep blues found in a night-time or polarized sky.
It's now my go-to camera for hiking, events, and anything like wildlife and other distant subject (due to the superior crop-sensor reach with telephotos added). All in all it is a great compliment as a backup with additional unique talents of its own that add value to my equipment lineup. I thought about the 7D for that purpose but in the end the flip-out display won my heart!