On Tuesday morning I submitted this blog to StumbleUpon. I've played with it a few times but never really tracked the effect.
In the next 48 hours I get 450 unique visitors and over 900 page views from Stumble. Unfortunately, it dried up as quickly as it appeared. So far today we've only seen 18 visitors from Stumble.
Additionally, the extra visitors didn't turn into revenue. Normally when visitors are ready to leave my site they have a choice of many outgoing links, of course this includes advertisements. Stumbler's however tend to use the toolbar to bounce to the next website. Of those 450 unique visitors, only one of them clicked an ad, and I can't even be sure that one came from Stumble.
900 page views... 450 uniques... total revenue for the two days $0.63.
Not worthless, but not the gold mine it might seem.