Been using them as a place to get some stuff done.
I have very mixed feelings.
The problem is the sheer diversity of the offerings and the people on the site.
Diversity isn't always good. It could be just a big mess.
The basic concept of the website is good. It's like a forum where you can meet lots of people who are interested in selling their skills.
Your funds are protected because of Fiverr's system. Sellers can make conditional offers, and the system doesn't release payment until all revisions are done as per the contract. Also they don't release the full files to buyer until buyer approves the contract, so buyer can't take the work product and run off. Buyer has to pay first (just that the money is held by fiverr)
However like everything online, they take all types. You never know who or what you are talking to. Does somebody really have this skill set? Is this person just offering to do something that he might not be able to deliver on? I've seen people with like 10 and 20% positive ratings because they screwed up so much. Talking to some people I'm pretty sure they know nothing but don't want to admit it, while other people who advertise their super skills, readily admit that they don't know or can't do something unless you agree to pay them a lot and let them experiment, no guarantees.
This is a website where selling yourself is practically the entire name of the game. Exaggerations abound. Lots of people are more hot air than real skill, and charges/ offers are all over the place. A lot of base gigs look cheap ($5 is very common), but many gigs run pretty high once you start talking. And that makes me question, because it seems as though some experts take a lot more time to do something than they should if they were genuinely experienced and skilled with the task.
And some people with huge numbers of good ratings are very suspicious too. The system doesn't seem to allow fake reviews from un-verified 'buyers' unlike some other websites, but not everyone with tons of good reviews comes across as being a professional seller. Sometimes you wonder, what were the buyers thinking?
Since most Fiverr sellers are just doing this as a second job, turnaround times are very mixed and often people make promises they can't deliver.
I would use fiverr again, but also don't have much loyalty to them. My gut feeling is that most of what they offer, you can do yourself nearly as well just by youtubing or googling. Sure, they save you some time, but it's not great value considering that you need lots of communication and negotiating and back and forths before the work is done, so not as if you save 99% of time for a modest cost.
On a personal note, it seems as though many people on fiverr are less humble than people on geekhack. There are a lot of people with very high technical skills on geekhack, who post their projects and talk and you know they are real smart and capable people. And they are humble and helpful. On fiverr people are more concerned with selling themselves, so the tenor is more inflated and it really irritates when you contact someone who turns out to have far fewer skills than he promotes himself as having. I know they're mainly a services selling site not a hobby site, but even when comparing apples and oranges you can distinguish between sour tasting oranges and sweet apples.
I think Geekhack should open a Classifieds for services and skills, and let people buy and sell services too. I bet someone like Haata would command top rates for tech services, and he wouldn't need to self-promote to get interested buyers. (I am not referring to the Artisan Services section which is all about people making and selling homemade keycaps - I think we should have a general section where people can offer CAD design, offer website editing, or whatever.)
