In a nutshell, I'd review DarkStar, our Vent Host, as outstanding. Our experience has been phenomenal, there has been no downtime and the transition to Ventrilo 3.x was smooth. We haven't had any problems with the service.
Deciding a Vent Provider
Originally I bought service from three providers, in an attempt to determine which one was best. I don't even remember the other providers I tried, but I felt the most comfortable with DarkStar at the time - from the getgo I had warm and fuzzies. The Ventrilo server was set up instantly and has been up up ever since.
One thing I remember overlooking was codecs. Not all Ventrilo providers allow you to use high quality codecs and some make you pay more. DarkStar happened to include the premium Ventrilo codecs for free, a value which cannot be overestimated. The lower end codecs just don't hold up to the high quality "premium ventrilo codecs" that DarkStar provided.
Reliable Ventrilo
Obviously as a serious raiding guild, we needed a quality Ventrilo server with outstanding uptime. DarkStar Ventrilo has been up since we signed up, I haven't noticed any downtime. For Ventrilo to be useful, you have to be able to use the Vent server whenever you need it. Uptime is the all important factor in deciding what Ventrilo provider to go with.
DarkStar Review
The first thing I did when I decided to write a review for DarkStar is look for other reviews. The first DarkStar Review I came across was a long list of positive things said by their clients. I wish I had known about the contest sooner though. I didn't even know they had a blog. All positive comments though, which is a big plus and I'm glad to know I'm not the only one who has had great service.