Just followed you, Emily. You'll find me here:
http://www.stumbleupon.com/stumbler/Indounik/ I add some of my own listings and treasuries and sometimes those of others and it can be hit and miss whether StumbleUpon opens the gate on driving traffic to those listings or treasuries.
Once when I added an unusual cab, StumbleUpon sent about 500 people to look. The views kept going up at a somewhat dizzying pace but I can't say that it translated directly into sales.
I also add a number of other subjects in which I'm interested - mostly to do with beautiful Bali, the inspiration for my product lines. I think the trick is to be diverse and not make it all about Etsy or all about your own shop and products
I'm not a supreme regular on StumbleUpon but I do enjoy using it. And I can say my shop stats show it regularly drives traffic to my shop.
This Mashable article inicates that StumbleUpon drives 50 per cent of social media traffic to the rest of the web - ahead of Facebook and Twitter.
http://mashable.com/2011/08/19/stumbleupon-social-traffic/Anyway, I hope you enjoy it as much as I do.