New venues are always a mixed blessing. None will ever have the buyer "gravity" that eBay does -- it's a mature market, and all the early players retain dominance no matter how much they suck -- but on the other hand, it's easier to stand out at a smaller venue, to be a big fish in a small pond so to speak.
As far as HipSwap goes, I have to say I love the layout and general setup (aside from the infinity scroll, which I despise everywhere and wish the person who came up with the idea would get herpes; but that's a minor design issue.) Reading your review, the only automatic deal killer for me is the idea that HipSwap takes the buyer's money and remits it to the seller after their cut -- however, looking at HS' own description of their service, this does not appear to be the case.
Unlike most other little sites trying to compete with eBay, I notice that HipSwap Link hidden: Login to view, having been funded by Greycroft and other notable venture capital funds. While that doesn't assure success, it at least means that the people running it are not total idiots and/or serial thieves, since most VCs will not drop millions of dollars into somebody's basement-based pipe dream site. It's also had a good bit of positive press and online buzz.
And people are definitely starting to notice it -- look at Google Trends' search volume chart for them:
And they're spending next to zero on advertising (at least, on AdWords and other online stuff I can look up) which means most of that buzz and traffic is coming in from actual user interest.
I dunno, I usually crap all over sites like these when I hear about them, but HipSwap really seems to have a lot going for it. As with many other sites that have no listing fees, it can't hurt to try them.