I sold mine for $600 a few years ago. I'd buy one in a heartbeat for $400, that would be a steal. Expect to pay $550-$700.
1) the iron sights are useless for anything except illustrating why a long sight radius is good
2) they are heavy, I remember 11 pounds or so
3) they are actually pretty accurate, the long barrel bullpup configuration is unique but functional
4) the fact that they take M16 mags is a plus.
5) they are pretty reliable. I never had a malfunction from mine. They use a piston gas system that is very similar to the AR 180 so if you don't like the M16's DI design you might like that.
6) the reciever/stock is made from aluminum and gets hot with sustained firing
7) trhe triggers can be smoothed out some but will never be crisp or light due to the design. You can get used to it.
Overall, I'd say it is a novelty that can be pressed into practical use if needed but not a viable option to an AR 15. I'd rather have one of them than a mini14 though
the most recent gunbroker auctions that sold were
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=230467709
$639
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=241287602
$750
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=246432722
$700