I've bought 3 lenses from ebay. A Minolta 50mm f1.7 prime and a Minolta 70-210 f4. Each of them cost about £75, so it was a risk, but a smaller one. Both arrived in good condition and are great.
Even the most expensive lens I've bought was only £130 for a Sigma EX 28-70mm f2.8 . Which is an older lens, but it was in good nick and it's been great. It's my walkabout lens.
When I'm looking at lenses on ebay (quite regularly
) I check the sellers feedback; have they sold camera stuff and lenses before, have there been any issues, have people been happy with the lenses.
Also check back to see if they had previously bought the lens you are looking at on ebay (ie look at their buyer feedback to see what they've bought). If they've bought the lens recently and are now selling it on quickly, ask why? The ebay listing may explain (ie the bought it for a holiday or an event or they are upgrading) but worth asking if it doesn't say. If they are a trader, then that's fine, but they should be able to give you a good description of the condition.
So far I've managed to get some bargains and not had a duff one, but that's a risk with buying anything on ebay.
There are plenty of reputable camera shops that sell good secondhand stuff that will come with a guarantee and you can try them in the shop. For example, my favoured shop has this in it's Southampton branch:
http://www.lcegroup.co.uk/Used/Nikon-AF-S-18-200mm-f/3.5-5.6G-ED-DX-VR_58147.htmlOn the subject of "super-zooms" (lenses of this type), they are always going to be a compromise, they're not going to be as fast or as sharp, but you'll only need to carry one lens.
I had a 28-200mm Tamron for a while, but while it was kinda handy to have a jack-of-all-trades lens, it wasn't fantastic, although it was smallish, it wasn't light and half the time I wanted a better quality lens. So I sold it and got the 70-210mm which gives me constant f4.
If I just want to take one lens out and about, I will usually go with my Sigma 28-70 f2.8, which gives me good zoom range and low light capabilities. Or if I want something smaller, I will take my 50mm prime.
But, if you only have the kit 18-55mm lens, I would be tempted to say get a 55-200mm or 70-200 to complement it, perhaps from Sigma or Tamron and save the money for a 50mm or 30mm prime lens, which will give you something good for low light and better quality glass.
