Exactly, it's powerful enough that it can run stuff like Spark, as well as real development environments for people who get that far. It's relatively cheap, so that schools, and for that matter, anyone who wants to have an experiment, can, and even if they destroy the device, it's not the end of the world.
Arduino's, and their clones, are a great way of getting cheap microcontrollers out there, but the development of them is a little intimidating for anyone use to the handholding of your average Windows app.
It does strike me, that the cost of monitors is now going to become a significant one, because even a cheap monitor to use with this device is going to be £100 or so (five times the price of its controller). I guess one of the advantages is, that it's relatively unlikely that any monitors could be easily damaged or destroyed using a Raspberry Pi, whereas the front end electronics could easily be killed by ESD or some electronic oversight.