I would agree with Holoedrain and say that if you are just starting it would be better to to use 2.5 as the interface is a lot cleaner and it is easier to find things than 2.49. I personally have moved to 2.5 exclusively now.

Most of the modeling tools are in place and with a couple of exceptions work as advertised on the packet, notable exceptions being the knife and bevel tools.

Bear in mind also that many of the newer tutorials seem now to focus on 2.5 exclusively. A couple of good sources are Blendercookie.com and Blenderguru.com. A viewing of some of those at blendercookie will give you a better idea of what to expect.

All versions though will run side by side, so if you get stuck, you can always revert to 2.49 to get the gist of things.