There have been a number of posts over on the DPReview Konica-Minolta Talk forum about people buying refurbished A2s. Generally the feeling has been that they are pretty good. The most important thing is that the retailer themselves is reliable.
The refurbs come with either 3 or 6 month warranties. You can purchase an extended (3-year) warranty from K-M USA on their web site (if you are in the US).