One of my Magento clients ran into a bit of trouble with their current hosting provider. Stability was not up to what it was supposed to be, there were security issues that raised concern, and support was slow and indifferent at times. The client is a retailer that gets significant traffic spikes during shopping season and when doing promotions. The infrastructure of the current hoster was not flexible enough to deal with huge traffic spikes in an automated fashion.
We decided to switch to a different hosting company to improve the situation. We looked into a bunch of companies and ended up giving Rackspace Magento Hosting a go.
This post is a post-mortem of a failed attempt to switch our hosting provider.