My personal experience within the last 7 years:
* Softlayer – the best option in terms of quality of service, quality of hardware, quality and size of the infrastructure (geo distribution, etc).
* Rackspace – nice, until you grow enough to get relatively locked in and then your prices start to go up, provisioning time suffers and their service turns into shit.
* Steadfast – provisioning times up to a week, basically a joke in today's world.
* Some German/EU providers like Hetzner – dirt cheap option with desktop-like hardware, failing quickly. Service is nowhere near SL level.
I could go on and on about those, but other options were even more painful.
I could go on and on about those, but other options were even more painful.