Blogger Sam Davis of Blasted Thing wrote a great mention of A2 Magento Hosting. He wrote:

Probably the grand-daddy of Magento Hosting!  These guys are proper good, because whatever you’ve you’re looking for (in terms of hosting Magento) they will do it.  If its only a small store you want, or a multitude of stores on your own dedicated server, they will set it up for you and it’s all ready to go.  I’ve used them and they are really great - and really well priced too, I should have a look at them if I were you.

The grand-daddy of Magento hosting, eh? I tend to agree. You can read the rest of his post here.