Nothing wrong with putting your kid in daycare when they are 2.5. It does depends on the kid obviously, some are more suited than others. I did this with my daughter when she was two. She used to go in the mornings, everyday. She was ok. Separation anxiety is bound to happen at the beginning, and I think its more traumatic for the parent than the child.

One thing to bear in mind is that your child will be sick a lot. When they first start they are exposed to all sorts of nasties from other kids and their immune systems will get a good work out. This is a good preparation for school as they build up their tolerance levels to germs. My daughter was sick every other week but shes fine now she is at ecole maternelle.