I don’t have experience with Rackspace, but, like the other commenter acangiano said, I only have good things to say about SoftLayer’s support for the past 4 years. Their customer service reps are quite responsive and can be reached either using tickets or phone. My issues were mostly addressed within an hour or two, even when it’s not during the normal office hours.

Rackspace user here. Be prepared to pay $$$$-their hybrid environment is not cheap, especially for servers with above normal specs. There are also (industry standard) restrictions on the network side of things with their VM's, which we weren't prepared for when we started. Lastly, if you're ever the target of DDoS attacks...good luck.

Previous Rackspace user here (we got fed up with Rackspace and finally got our own equipment for a song compared to our monthly hosting costs with them)... Yeah, good luck if you get a very common DDoS attack while on their network. Apparently their data-centers in general are large DDoS targets. We moved and have not had an attack since (and it's a big deal since we do e-commerce).

That said, out of any company I've ever been with their support was really good. Just understand you're paying like crazy for it.

There's also the Storm/Liquid Web combination.

http://www.stormondemand.com/ http://www.liquidweb.com/

My startup is designed around these issues: https://uptano.com

Every server you launch is connected to your own private LAN.

I only have experience with Rackspace (though I've heard consistently good things about SoftLayer), but my experience with them has been fantastic.

I've used both. SoftLayer in my opinion has faster and more price efficient offerings. Always gone with them and never regret it.