It costs a bit more but I've found it to be a really sweet piece of glass. All of my California shots were done with it (it's all I brought with me). On my XTi, the AF works better than any other lens I have. It's something that I think would serve you very well for a long time to come.
EDIT: If you plan on doing any outdoor work, don't forget the 82mm CPL. It makes for a beautiful combination.
EDIT2: This is transformed from RAW and resized for posting to show how it does a macro shot (no other processing). I need to get extension tubes! Look into the Iris:
Canon EOS DIGITAL REBEL XTi 70mm 1/60th F10 ISO100 Macro Capability Sample (70mm)
