I've bought the majority of my kit second hand and can really recommend it.
The thing about togs, the equipment costs a fair amount of money, so people tend to look after it quite well.
If a lens has been kept in really good condition, and you're saving a boatload on it by going second hand, I don't see why anyone wouldn't. I picked up my Sigma 10 - 20mm wide angle, 70 - 200 F4 L, 50mm F1.8 and 28 - 105mm all second hand, in some cases for less than half of the new price.
As for bodies, same thing applies, though be wary of older bodies and how high the shutter count is, how the body has been treated, if it were fixed for any reason and if so will that issue come back or will something else go?
Personally I'd take a second hand 40D over a brand new 1000D, though I'd bite the bullet and get a brand new semi-pro body or greater brand new(actually what I did with my 60D).
As for cards, they're relatively inexpensive so I'd get a few of them new, same goes for things like filters (unless you need an 86mm filter, then you kak en betaal!), spare batteries etc. Bags are a toss up really, if you see a good deal go for it.
My 2.5c