We have a large number of servers with SingleHop, and have been happy customers of theirs over the past 4 years.
If you're a tandem partner, you can get much better discounts than their regular front page. As always, the more hardware you have with them, the more discount you get and the more weight you have to throw around.
Never had an issue with them - always fast, always responsive and pretty much always available.
Singlehop was good for network and uptime. Support was great as well however we went through no less than 5 sales reps and each of them were less than helpful.
We have since moved our services to PhoenixNAP and have had a MUCH better response as well as partner program from them. They have really helped us take off and our account rep is constantly giving us feedback, tips, and special deals to grow our business. If you need further details, please feel free to ask.