The historical downtimes got reset when they changed to the new control panel, but I'm showing 99.60% uptime for http, 99.85% for smtp and pop3, 99.83% for telnet, 99.83%
for ftp since then on my largest site, very similar numbers for other sites.
That includes planned downtime. Among other things, they recently physically moved from one computer room to another. Planned downtime usually occurs in the wee hours of the morning when my users and all other sane people are asleep.
I wish I had that kind of reliability in my telephone, electric, and cable TV service, but hey, they're monopolies. Dreamhost has to hustle to keep webmasters happy - and while not perfect, they've done pretty good for my sites.