I just spent the last three hours getting two "free" computers loaded up with software that will work with our domain in our classrooms. That software will cost over $100. Despite the fact that the computers are brand new, they have only the typical specs of today's netbooks, even though they are full size computers. Let's just say, in my humble opinion: "Free is not always free, and free is not always worth it."
The key, I think, is minimum specs and to standardize, standardize, standardize. I always ask what do you want to do with the equipment and do we already have something that will do that?