I have been agonising for a couple of weeks now around what lens I should look at to upgrade from my current 18-55 IS kits lens as a general walk around lens for my 550d while I settle into a rhythm and decide on what kind of photos I enjoy taking more (and then look at getting more specialised glass).

After a ridiculous amount of research online I think I have narrowed it down to the Canon ??-85 but am stuck on deciding which one? Anyone with an opinion on if the newer 15-85 enough of an upgrade to warrant the $300 difference?

I am also open to any other suggestions (including any Tamron or Sigma options) but am probably looking to keep away from superzooms.

Any insight is appreciated