Hi,
well so far I have had a
350D,
30D,
1D Mark II,
40D and a
50D, and all have been good/great for wildlife in their own way but all slightly different if you know what I mean.
If I was advising anyone for a used body it would be either the 40 or 50D, but only if the 50D was available used, I don't think I would buy a new 50 over a used 40, esp as there is about £400 difference.
Let's look at each one in turn.
350D, would probably discount this one as a bit old now and AF a bit hit and miss for Wildlife.
30D, still a great camera, used prices at around £300 or slightly less, a good buy, AF is decent, noise is pretty good, but.....
A
40D can be had for around a £100 more S/H and it has better. faster AF to the 30D and has superior noise with higher ISO's.
The
1D Mark II that I owned was the dog *******s for fast AF, but you lose the 1.6 crop factor as it's a 1.3x camera, the AF is superfast, is precise and the images are great, a bit more noise using higher ISO's, waterproof and rugged for serious wildlife use, sling it over your shoulder and forget about it, used prices vary from £650 - £850 just now, I miss it but would only buy another one at the right price ie: £650 not £850
Now the
50D, a fantastic body, probably better AF than the 40 but not as fast as the 1D Mark II, but not by much, it takes a bit more work getting the images to look right especially if cropping at higher ISO's as the 15mp sensor starts to look soft when cropping too much, however if you can fill a large part of the frame and therefore saving on cropping , then it's a superb piece of kit but at a price with it being so new.
Here are samples from each body except the 40D as I only had it a day or so before giving it to my dad. The pics have been taken with different lenses, but at least it might give you an idea as to what can be achieved with each body.
350D - Sigma 100-300 F4 EX HSM
30D - Canon 100-400 F4/5.6L IS
30D - Sigma 500mm F4.5 EX HSM
1D Mark II - Sigma 500mm F4.5 EX HSM
50D - Canon 400mm F5.6L
Now looking at each of those images, can you see something significant, yip, the glass, each body takes good images, but the glass is what makes the significant difference, the image of the Dunnock with the 30D and 500mm Siggy is one of my best and probably makes you (and myself

) wonder why I got rid of the 30D, the joys of upgradeitis, although it does show how good the 50D is with the Canon 400mm F5.6L lens which is a third of the price of the Siggy, I just wish I had had the chance to try the 50D and Sigma 500mm combo before selling it.
I think what I am saying is this, if it was me with £1000 I would buy a used 30D OR 40D, (les maclean has a 40D for sale just now) and put the balance towards a decent lens
Hope this helps, now I'm off for a rest, my fingers hurt
Mike.
PS: I notice that Bob has recommended a similar move, he posted whilst I was typing this up, he know a thing or two about gear
