I bought a Tippmann A-5 from Dave1004 2 weeks ago.
Lets start with the good:
Responds to PMs very quickly: a BIG plus!
Reasonable prices
Free shipping
My marker arrived well protected and in good cosmetic condition that told me that he tries to take good care of his guns.
He gave me a free ammo belt since this was my first gun purchase.
There were two things that weren't as good:
Not really his fault, but it took 8 days to get my gun, but that's because I live in Michigan and He lives in California and also because the US Postal service is REALLLYYYY SLOOOOOOOOW. UPS would ave been twice as fast, but who am I to complain since he paid the shipping

. If you live on the other side of the country from this guy, asking him to ship UPS might not be a bad idea for you if you are of the slightly impatient type.
Also, when i got the gun it didn't work. Read this thread for details. It took me more than 2 hours and 6 gun strip-downs to find that the O-ring on the bolt had come off and had slid back on the bolt into a narrow spot. I later found that this wasn't the right O-ring at all. Once I replaced it, the marker worked like a dream.
I'm sure that this was an honest mistake, but I should have asked him to test the gun himself before I bought it, because he had said that it worked and it didn't initially.
Overall, a mostly positive experience. hope this will help somebody someday.....