Jorge - I'm super biased as the CrowdFlower CEO but we work really hard to make sure everyone gets paid and all disputes are resolved. We have a team of four full time people that do nothing but handle community support tickets and we've paid out many millions of dollars mostly without issues. We moved off of Mechanical Turk a few years ago because it was hard to give workers a consistently good experience there. You can see the twitter stream from our contributors and most of the comments are positive https://twitter.com/search?q=cfcomm&src=typd
We are definitely more expensive than turk, although we have big discounts for small startups that makes us comparable.
Lukas, I'm sorry I reacted so negatively, seems I was not fair and let me know if it's possible to use CrowdFlower, like start with a low non monthly commitment cost and go from there.
For your information, I am basically doing photo tagging, wondering what my costs will be, how fast jobs will be completed etc.
Looks like Lukas might have missed your response but I can jump in. We definitely love to work with the little guys, too. Nothing is more interesting than the use cases that academics and startups come up with. You should reach out to Lukas via e-mail (he shared it elsewhere in this thread) or our sales team (http://www.crowdflower.com/platform-plans) to talk specifics.
We've also got a trial that will let you process 5,000 rows of data without having to worry about a paid plan. It's not time limited, either, so you can take as long as you need to go through those first 5,000 photos of yours.
We are definitely more expensive than turk, although we have big discounts for small startups that makes us comparable.