Well, the Basic Stamp is/was a good tool for the right job, for example you are building a robot. You don't want to learn about the internals of a microcontroller, or electronics even, when your hobby/goal is a servo controller or something.
You just need that black box controller.
I wouldn't use one ( unless I had to ), the price is too high, when I can rather more efficiently hack up something with my own uC. The newer BS stamps (>BSII) dont use the 20Mhz/5 Mips 16C series running at whatever the BS onboard clocking ( something around 16Mhz IIRC) , but the SX series which for 50MHZ will give you 50Mips. I don't know the actually clocking/ basic lines/sec though.