I've tried it... here are my thoughts:
1) Far too US-centric. If that is your market, that's good, but I like to stay in Canada.
2) Shipping to and from the US is a bonus, but I found that getting tracking and help from the drop shipper was a pain... they seemed so busy all the time, and would only answer emails 24-48 hours later... I like to provide my customers with better service than that.
3) You can't actually see the item before you ship it... if a seller asks you a question, what do you say?
4) Inventory is hit and miss.
5) If you're selling it, there are probably 30 others on eBay doing the same.. and you can never seem to make your prices as low as theirs...
Overall, it's an interesting venture. You need the right product at the right time at the right price...
Joe