OK, so I guess I'm probably one of about a billion people considering an upgrade!
Anyway, I currently have a 40D which has served me well and which I enjoy using. However, there are a couple of things which consistently annoy me about it:
1) it seems to miss focus sometimes even when focusing in good light and on very simple subjects (i.e. not moving). I had it the other day when I was taking pictures of people at a wedding (not as the official tog, I might add!) and there were a number of photos that would have been great, except the focus wasn't nailed. Really frustrating! It's not off by a mile and it doesn't do it all the time (so it's not a back/front focusing issue - although I've tested my lenses, just in case) but it would be great if it didn't happen so much. I know that pretty much all cameras will have the occasional "moment" when the focus doesn't quite happen, but it would be nice to minimise it.
2) The screen on the back can't really be used to check sharpness very well due to it's resolution (or lack of!). Couple this with the above issue, and it's a real annoyance.
I realise neither of these issues are particularly serious (given that I'm not a pro or anything) and that even if I upgraded and managed to avoid them again, it won't make me a better photographer - but it would be nice to have fewer pics that cause an "aarrghh" moment.
One of the main lenses I use is the Canon 17-55 2.8, so I'd probably want to stay with an APS-C sensor for the moment. I've been toying with the idea of a 70D which I believe has a much upgraded focusing system and a much better screen than the 40D - along with all the other upgrades...sensor, DIGIC 5, etc. (I've heard that some people have issues with the focusing but from what I can tell, that's not the norm). The other option would be a 7D, which I believe would probably be a similar kind of price point.
Any thoughts or recommendations...?