We are using bluehost.com right now, and so far so good. They are straightforward about their capabilities.
On a side note, if you are considering siteground.com, people are echoing our experience and would not recommend them for a moodle install. We currently also have a moodle install on their servers.
They believe that moodle queries hog too many server resources. And they have limited our account to only 10 concurrent connections because of that.
I don't put much faith in their moodle page which touts them as one of the worlds best moodle experts, as I recently learned among other defficiencies, that they had our moodle install with a memory limit of 8mb (the bare minimum is 16mb, they did increase it after we pointed it out, but that was after 8 months of having performance issues) and also are using older versions of postgres
(7.3, and moodle requires minimum of 7.4, which they refused to upgrade stating that it is not compatible with their server installation)
There are other discrepancies I have found as well, which are not within the scope of this post.
Though their support is prompt and polite, they are not helpful with moodle as they claim in their moodle support page. Whenever my site is down, and I create a ticket, the best support they have given me is to recommend that I upgrade to VPS. Its come to the point where its become monotonous.
Something I liked about bluehost.com is that nowhere on their site do they claim anything about moodle expertise. And even bluehost.com support was straightforward enough in telling me that I will have to support moodle on my own within the limits of their server parameters. We appreciate this straightforwardness, as it prepares us beforehand, rather surprises.
This is not what I got from siteground.com though. Siteground.com support staff were very gung ho about moodle, constantly giving me the impression that they know a lot about moodle, initially. After the 30 day period, their expertiese vaporized, so to speak.