I upgraded to the Tamron from one of the kit lenses that came with my Nikon D5000 and I'm so pleased I made the investment.
These aren't the fastest (wide aperture) lenses available but to get anything better you can treble the price of this one so it really wasn't an option to look at the fancier models out there. Image quality is staggeringly good and mounted on a tripod for a bracketed exposure the Tamron gives superb results in even the poorest light conditions.
Having the extra width of frame that a 10mm lens affords is really handy for the style of photography I enjoy (urbexing) and it has opened up a whole new world of possible shots that I wouldn't have been able to acheive otherwise. It even has the built in motor for the auto-focus so a non motorised body like the D5000 will still work fine with it.
If you can't afford to spend or justify £1000 for a lens then this is the best I've found.