I have used them for over 3 years. Superb service.
There is a basic rule to follow if you intend to get as movies as possible: DO NOT return more than the number of movies on your plan, more than once a week. If you have the 3 movie plan, do not mail back more then 3 per week. This gives you 12 movies a month. If you try to exceed this amount, at first, it will work - maybe for a month. Then Netflix computers will start to 'throttle' you; this means they will start delaying mail outs for a couple of days or even 3 days, after they get your movie(s) back. It will cause the service to suck. I have tried it out several times over the years and that was the result. Follow the rule above and you will have fast, excellent service.
-Chris