changed the title and names in your post to be correct (fLight club).
anywho. been to the place several times, but never bought anything. honestly, prices there are just too steep because of the extra charge they put after getting your initial price. i'll give you random ratings on how i see it though.
reliability - not too high. like i said, unless it's rare, you probably won't sell for a while unless your price is really good.
profitablity - everything you put out is at the price you set + the percentage of what flight club takes, so this is all on you.
easiness - pretty much same as reliability. it all depends on what you're selling and at what price. but if you mean easiness as in the process of putting it up for cosignment, then i'd say it's pretty simple. rules are set up at their website (vintagekicks.com)
hope i might have helped a little somewhere in that long post.