I've used Odesk.com with good results too, I was very selective.
I looked for individuals as opposed to groups or agencies, I avoided 5 out 5 star (100%) ratings and headed for better than 2 and not better than 4, I chose people who had experience in the technologies I needed, almost invariably they overestimated their ability, but I do that too, that's just human.
I chose people who had been with Odesk at least 6 months and not more than a year or so.
I checked that they were able to speak enough English to understand job requirements, don't expect impeccable grammar, this is after all the twenty first century!
I made very clear the commitment required and we discussed at length the time they would have available and what factors would affect that, every one I worked with had a 'day job', so my arrangement was that they would be required for a maximum of 10 hours in any week and we would agree in advance realistic schedules.
With those caveats in mind go for it, it is an enlightening experience to work with people from around the world, all so far have been honest and hard working, I pay everyone the same wage which is 10% or so above the minimum wage for my country, a rate that I have had to work for numerous times in my life. Invariably their living expenses are lower than mine and all have appreciated the income, I have a freelancer who has emigrated to avoid persecution and another that had 11ft of water through their home but was back online within 5hrs as they had taken the computers to the attic space, instead of a gift of charity I made an advance so they could rebuild their home and the advance was paid of with labour at a slow rate so they could maintain their current commitments.
We live in a global community, and it is truly awesome :)