Lego is a great toy and Mindstorms is a great robotics/embedded control education tool. As well as educating it also can be used as a very effective prototyping system - but do you feel a little ashamed when you end up using the prototype for real?
There seems to be something a little wrong with having a brightly colored plastic gizmo in charge of something essentially serious. Well if this is the case watch the video which shows Cambridge University biologist using Lego Mindstorms to automate a lab process. They built what look like toy robotic cranes to dip samples into chemicals.
For some reason the Lego doesn't look out of place and it doesn't look like an amateur attempt at saving money either. Perhaps it's the glass and the lab environment that makes it all seem reasonable but it also makes the case for using construction kits to do serious work. After all, physicists and engineers have long use metal construction kits like Meccano to build all sorts of equipment - including computers.