I host with ServerMatrix and their parent company, ThePlanet.
Their support isn't the greatest, but it's not the worst either. If you have an issue you can call a toll free number and get a tech guy on the line to help you right away. It's their online support that's kind of lengthy. They have a 'ticket' system and it usually takes a couple hours to a day to get someone to look into your problem if you don't call.
Their regular ServerMatrix servers and TotalControl servers run on an awesome network. They've got like 6 different backbone providers. Their MatrixExtreme servers run on Cogent, as has already been explained.
I don't use a MatrixExtreme server and I don't intend to in the future. BW quality is important to me, but that doesn't mean they're not good servers for the price.
I do recommend ServerMatrix and ThePlanet if you're comfortable running your own box. If you don't have any *nix or networking experience then go with something a little more friendly. You must be able to configure apache and ftp yourself etc.
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