I bought a 16GB refurb from Best Buy and it is working perfectly. I may upgrade to a 64GB, but I have been reading a lot lately and I have seen more bad reports from the 64GB PBs than any other size (I could be wrong though).
I bought a refurb 64 GB Playbook from Amazon Warehouse. It was practically new, just lots of scuffing on the outer box. It has the infamous bulge on the back, but that isn't an issue since I have it in a case, and quite a few stuck/dead pixels on boot, that disappear once things are up and running. It cost me $300, so this is a better deal money-wise.