So far I've been with NFo since September '05. When I put up my initial 16 slot server I was blown away by the low pings. They were the lowest I had ever had in any server, and it was great because it was MY server.
Well, my clan has grown quit a bit since the intial creation and I now have 2 servers running. A 16 and a 24 man. Perhaps one day we will move up yet again to three servers. That third server will be with NFo.
Any time I had any sort of troubles with my server, the NFo support guys were there to help, and they did it fast. There was even an instance where my connection was taking abnormal hops across the country and back, and NFo got in touch with my ISP and got it fixed!
Great service, great servers. Can't go wrong with these guys.