Hello!
I was in my school's robotics team and we were required to use the Lego Mindstorms kit to build a robot for the area competition. I did not get to use it for long, nor am I the mechanical person that wanted to build the body itself-- it is very easy to use. I agree with above posts, the Mindstorms kit allows you to create great robots without needing to build your own platforms, cutting and drilling every time. Just snap on.
It's been touched on that the IO lines aren't enough, but there are ways to use more than add on from one IO line (you'll have to read up on that). Aside from that, the programming for it is all graphical, and I've heard you can find a way to get real programming language compilers for it.
Anyways, I think the kit is a good choice! Good luck,
Omar