I personally won't go for a rig if the model isn't appealing, specifically in the face and hands. I don't care what cool controls it has, I feel like a bad design can really hurt your animation... That's just me though, lol. For the rig itself, what I look for is pretty simple: Flexibility in the face, IK/FK switching (I'll settle if it doesn't have matching, no biggy), stretchy limbs, good believable deformation, and nice hand controls (I like to be able to control the fingers myself, and not have them automated).
So, this brings me to my point! I feel like to get what you want, the best thing you can do is either learn how to do it yourself (Which I prefer), or find a good rigger, through a LOT of research, so you don't waste your money, lol... If you don't want to learn how to do these things yourself, can't pay someone, or don't know anyone who can do it as a favor, I recommend this AMAZING tool!! It's not THAT expensive either! Of course you'd need a character model though.
We used this tool when I worked at Lightstream Animation Studios, and I really liked the flexibility I could get in the face. It's not perfect of course, but it's a quick way of getting really good results, with not a lot of effort. Click the images to see some cool videos demonstrating the tool.Visit the website and check out the other videos.
Here's a short film where the characters were rigged using these tools!