I've used it for a few years, I have it running on two PC's now, I think it's a great tool. I use my bank deposits as the real gauge, but the quick reports per program, covers almost all the programs I'm in (and I'm in lots).
In fact I use
http://www.unifiedstats.com/programs/index.php that page to signup to most new affiliate programs, because nobody works as hard for free for me as John does at Unified Stats.
There are times when he can't provide lightning support, but it's free! The big problems are usually solved quite fast.