Well what lenses do you already have and why? What lenses do you want in the future and why? Bit more info on what you shoot/use them for would also help. If you just have a kit lens, then I would suggest a 50mm prime to get used to shooting with shallow DOF and low light use. I don't think you will regret it. It would open you up to a lot mor ein photography than adding the 17-85. yes the 50mm is restrictive as a walk about lens, but it does make you compose subjects better and think a lot more, but it's dead light, dead compact, dead cheap and dead sharp.