Ive been really wanting an AR-15 really bad. I put an ad on Armslist the other day wanting to trade my Romanian WASR 10/63 Ak-47 for an AR. Today a guy offered to trade me his DPMS Ar-15 for my AK. Is DPMS a good brand?
The WASR-10 is not exactly the pinnacle of AK-47 design. Then run $450 "new" from Century. I think fair MSRP for a secondhand WASR-10 would probably be in the $400 range. Don't get me wrong, I have a WASR-10 too, it is a good shooter in fair condition, but there are nicer AKs out there which haven't been chopped up by Century or converted from single stack mags to standard mags.
The DPMS AR is an entry to mid-level brand. I'd have to know more about the specific components in the AR to know more about it. Still, a "vanilla" plain lower with parts kit installed and M4-style stock is probably going to run about $100-150 new and the cheapest DPMS upper runs $384 new on Midway.
So, at first glance, you're making out pretty well. However, consider that you're trading an AK which you know works for an AR of uncertain pedigree. The seller may swear up and down that its a great shooter and you may find that there is some sort of issue. I'd be sure to function check the weapon and if possible field strip it before swapping.