I went for the 18-250mm F3.5-6.3 DI II IF Macro, S/H on Ebay.
To be honest i didn't expect to get very good results with it but its been a pleasant surprise.
Tweak the picture settings on the camera and you get very good results, i use mine on a D90. I have stored settings now for all the lenses i attach to make it easy.
Quite a bit of distortion on the wide end but nothing that can't be fixed if your that bothered about it.
I've found it very useful and has been on the camera for weeks now, i really like the focal range it gives you.
I only take it off when im out to put a 500mm mirror lens on if im on a wildlife mission, but its good for that anyway if your fairly close.
Auto focus can be pretty rubbish if you catch it out, but pre-focus on something close to where you need to be and its fine.
You can always go manual
. Also you can lock the zoom at the wide end as it will creep other wise.
I think if your on a budget and need this sort of focal range its a pretty good option. They do a newer 18-270mm but i don't know what that's like.
Here's a few pics taken with the Tamron, they have been through Photoshop but nothing too tweaked.