I've been using the Yongnuo flashes (2-YN565EX and 2-YN568ex)and YN-622C transmitter/receivers for over a year now, and have had virtually no problems at all. They have been reliable and have given good results. I regularly use ETTL, except when in a studio.
The only problem I've had is with the YN568ex. When I had a beach shoot, in full sunlight, I was using them for fill. But on HS, they tended to overheat in the direct Caribbean sun after 5 or 6 flashes. It wasn't a big deal. I just added a neutral filter and continued without HS sync (1/120 shutter speeds). But I have no idea how the Canon speedlites would fare in this extreme, either.
Certainly it is more convenient to use a single flash rather than a flash and a receiver combo. But if budget is an issue, this combination has worked well. I certainly can recommend it.