I suggest buying the PIC one in the Evil Genius series
It's much cheaper to start developing for
Don't get me wrong, parallax make some cool looking stuff, but it's way overpriced
I would say these Basic Stamps seem to be good for people who want to learn from half way up the ladder and want lots of functonality for very little hardware and simple code. However, I have never tried them.
PICs and 8051s are often heralded as the things to go for, for learning at least.