I think the letter puzzles have an 80% solve rate when ran through several OCR cloud-products. There was a rather interesting paper I read about the bypass.
I've used deathbycaptcha before, and it's a pretty decent service.
Yeah, the old text captcha ones were easily outsourced, and several places had around a 99% solve rate. Never used one myself, but know that it was very easily bypassed for cheap as mprep hinted. The way that this particular "exploit" works is by downloading the audio, and then identifying what the audio is saying automatically. This could probably be outsourced, and I would bet there are services offering this. However, what I imagine a lot of them are doing is running through a automatic speech to text. I don't know how accurate these are though, and they may well be outsourcing them.