Maybe you should wait a little bit. Since the ipad3 is coming out, who knows how low the ipad2 will go down to. Right now the new iPads are going as low as $70 dollars/refurbs for $80. So maybe a little more waiting might bring it down to your price..and mine!!
I've never done it, but I'd say just use common sense. If it's too good to be true, it probably is. I'd say eBay is more trustworthy since it's monitored, unlike Craigslist which is just a place to post your own ads. Make sure that the iPad works and doesn't have any problems, etc. Craigslist has its own list of tips and things to watch for on their site. Good luck!