To be honest I retracted my recommendation of Site5 in another thread
My gut feeling is still that they are an excellent host fighting hard to get over their growing pains, but due to restrictions in their terms of service getting tighter and tighter, for a medium to large Moodle install I don't think their shared servers are the best option.
For a start up operation I think you could do a lot worse. They are bringing back VPS soon and hopefully soon after that dedicated servers. Unfortunately, I can't wait much longer and will have to move to another host for a dedicated server (as stated in the other thread, if they had dedicated servers I would definitely stay there).
They have recently brought back their Multisite
plans which are excellent (basically reseller account functionality i.e. you can set up sites as you want to do so that for all intents and purposes they are unique sites rather than domain pointers) with the Multisite Dynamite plan being amazing value.
Although they are now limited in the quantity of sites you can set up this way (they used to be unlimited which is why I am still on my original plan
) you can still use domain pointers within those sites too. So, say you go with the Multisite Dynamite plan you could set up 5 sites and have multiple domain pointers within those sites. I think that may be a cost affective way of getting started for you (US$99 for a year or US$149 for two years hosting).
Just ensure you read and understand their TOS and decide if you will be able to operate within them in the short-medium term while you get established. Hopefully they will get the tech support ramped up again and start offering VPS and dedicated sooner rather than later.
Bottom line is that I still think they are an excellent host but not necessarily suitable for medium to large Moodle installs.
Good luck with your plans