By the way, a cheaper way to improve your photography (whatever your lens) is to get hold or a decent tripod. If you see a scene and feel it's worth the bother of carrying the weight, getting your kit out of the bag, setting it up, putting up with funny looks from strangers etc... then it's likely the picture IS worth taking. Also, the tripod will help you stop and think before you take it, which always helps (even if the subject is moving sometimes... )
Some examples of mine, which I couldn't have done without my new tripod (my old one wasn't solid enough):
http://www.flickr.com/photos/mazu_92/6583116571/
http://www.flickr.com/photos/mazu_92...n/photostream/