There's a lot going for Maxminis.
But be careful.
There's a certain few folks there -- very few, but some of them are prominent on the site -- who go out of their way to fleece newcomers who don't know the relative values of the miniatures. Make sure that you go into any deals armed with that knowledge. MaxMinis itself has tools to help with it, including price guides maintained by Zenako and indexes of relative popularity based on actual MaxMinis Have/Want stats. (The price guides are easy to find. The indexes are hidden pretty well. You'll want to use both in combination for the best gauge of value.)
In addition to the few problem traders, MaxMinis actually has a policy that people aren't permitted to point out when one trader is lowballing another -- usually new -- trader. It's this policy, along with one moderator who is both a liar and a cheat, that drove me away from MaxMinis, despite my standing as FAQ Keeper and Top-Ten trader.
All in all, though, if you go into the site with eyes wide open, and you're not some dumb Do-Gooder (like me) intent on protecting new folks from predatory traders, you can't beat the site for trading usefulness. There are other sites and mailing lists out there, but none has the volume or resources MaxMinis has.