Typically, you will get a response in around an hour; however, it has been known to take anywhere from 10 minutes to 2 days. The support staff are very clued-up, and you will almost always be satisfied with their knowledge and assistance.
I have had no more than a few hours of downtime over a period of 2 years (which is excellent), but some people report much longer outages. Much depends on the server you are on. As with all shared hosting environments, one must expect a certain amount of downtime.
DreamHost do not manage any of my domains, yet I can use all the options. Subdomains, anonymous FTP, shell access, email - the whole shooting match is available as long as you point to the DH nameservers.
You can have an unlimited number of domains, each with an unlimited number of subdomains (or even subdomains of subdomains). They all share the same disk space and bandwidth, but each can be throttled and controlled according to your needs.
Simon Jessey | Keystone Websites
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