Our site, NoSweaters (<a href="http://nosweaters.com" rel="nofollow">http://nosweaters.com</a>) started marketing on Stumbleupon's lowest click rate ($0.05/click) right after the Black Friday weekend. The start was slow. We garnered essentially the clicks we paid for and nothing more. Further, there were a lot of hiccups in the process, as we waited for approval for the campaign, which seemed to take much, much longer than other venues (read: Adwords).<p>Our target market, we decided, was women aged 15-30. From our exhaustive studies (aka, friends and family cajoling) we gathered they were the most enthusiastic users. We set up a custom front page for Stumble users to introduce them to the site.<p>We did this for Monday, Nov. 28th, Tues. the 29th and on Wednesday, we got caught up again in an approval issue, yelled at SU on Twitter, and all of a sudden we got blasted with organic traffic late Wednesday night (the 30th). Our daily visits went from 100 paid to ~20k unpaid hits a day for a solid week. After that, the traffic dropped off like a stone.<p>In that time, however, our bounce rate was only about 48%. We believe several factors account for this:<p>1) The main page was little more than an enticement with easy click through to the meat of the site.<p>2) The site was very appropriate for the time of year (a gift help site in the holiday buying months)<p>3) Our target happened to be spot on (we think).<p>We were also running a contest at the time to help drum up users and usage. Top users would receive Amazon gift cards.<p>All of these efforts yielded over 300 new users and more than 2,500 new "questions" (our site is a Q&A site for gift ideas; "asking a question" currently requires nothing but an email address).<p>From a purely return-on-investment perspective, we can say we were quite happy with the results we got from Stumbleupon. We're definitely suspicious of their methods of how they deliver organic vs. paid traffic (seems they've got their hands on spigots). We paid about $40 for the equivalent of 160K visits, and we got a ton of new content, and some very focused and dedicated users.<p>We've got a ton of test and usage data that we can now mine through to figure out what our next changes should be. We have very active involved, non-friend-or-family users that have given us very valuable feedback on what they want to see from the site. All in all, it's a great utility for a site trying to build itself, but I question its value for an established site (vs. blog posts or other SEO efforts).<p>If you have any questions about our experience, please don't hesitate to chuck them my way.