I'm also in favor of buying tools as needed.

The things I don't like about kits are that there's always something I'll never use, and it's hard to add stuff to kits, especially the ones the with custom cases. The kit is the kit and that's that.

I started out with a multi-tool, added a pedal wrench, chain whip and cassette lockring socket (all from Nashbar) to go with my existing socket set, and a chain tool (Park). That and basic homeowner tools kept me in good stead for years. I eventually supplemented with a set of P-handle wrenches from Nashbar. The Nashbar tools are perfectly fine for the amount I use them.

Since then I've added crank pullers and BB tools, (both Park) a torque wrench (Pedro's), a "torque key" (Giant), and I bought a set of hex bits for my changeable-bit screwdriver (ServiceStar Hardware).