Verified answer

Best is a matter of opinion and hard to give a real answer to that, none of them are that perfect and would probably actually take a lot of shopping around.

Maybe try some of those at the upper ends of vote sites like these:

http://www.xtremetop100.com/world-of-warcraft

Although I suspect their position there is likely largely due to sizable populations and not necessarily a guarantee of server quality. Molten always at the top though I've heard crappy things about them...but to each their own.

I can only personally speak about the one I use since it's the only one I've ever tried...though I think it's quite good and been there for three years with no intention of leaving. Not perfect, but they've always made it a work in progress to try to get what's broken working and I've certainly seen it improve over time. Also 3.3.5a, links on my profile.