I bought this and 10,000 pins for about $32 out the door. My first experience with a harbor freight nailer about 8 years ago caused me to sell it an immediately buy a porter cable.
I don't do much pinning, so I thought this would be OK for my needs. I've only tested it out on some scrap cherry moldings and maple, and it works well.
The only complaint I have is that it will leave a small dent on the wood after you shoot the pin if you don't hold the nailer at just the right angle. I would guess that if I spend $150 more on the grex, this problem wouldn't exist.
In all, I'm happy with the purchase. If I were to shoot more pins, I would spend the cash and get the better nailer (grex), but for the money you can't go wrong. If you don't have a pinner and the work of filling 18g nail holes has you thinking, don't hesitate to pick one up.