Strangely enough, I was tagged (surprise!) for a presentation about tools at this week's bike club meeting (my friend asked me to help out... when he started the presentation). The upshot is:

Buy tools as you need them. Tools that you don't need are just dead weight.
Buy the best you can get- they'll pay for themselves by not stripping screws or bolts. The very best (Craftsman and Snap-On) have lifetime replacements for when they wear out.
Care for what you have- if you break something, it'll be at 10PM the night before the big ride.
Harbor Freight sells usable hammers. Everything else is crap.