Haha, actually I'm one of those who got a Mindstorms for X-mas. I already had a few Arduino's.
The cool thing about the Mindstorms (IMHO) is the snap-together, give it a try on a whim aspect. They do have more advanced programmers for the MS that are C based, although I haven't tried them yet.
It is kind of limited, with only 3 motors/4 sensors stock, BUT... if what I have gathered so far is correct it speaks I2C, so there is potential to be in command of a lot more.
I think that's how the stuff at www.mindsensors.com works. It looks like they have a motor multiplexer to add 2 motors and a servo controller to control 8 servos.
I don't know... it's all just tinkering, LOL. Just a different flavor. 