My experience with fiverr is so far positive, I've set a Gig there some weeks back: I'll tweet about your service to my 18000+ followers (I follow less than 70 peoples) for $5 , it works really good for me: I'm $525 richer since then, but the most important thing, I've learned to deal with customer support, you can't imagine how peoples act even if they just pay a voucher for a service (I guess even if it's free), so no matter what they pay, and how great the ROI is, they will still ask for more, some poeples actually behave like they just hire you full time for $5 , that's the best thing I learned from it (customer can be really rough), and it also helps me validate an experience about twitter advertising and followers behaviour (a couple of peoples complained about the ads, and 1 or 2 unfollowed me, but otherwise, all ok)
I can recommend the service, but you really should know what you are paying for , it may have some Value if you really know what you are doing and you could have a lot from $5 , if you're lucky.