I've been with DH for 4 years. In the beginning there was some frustrating downtime, but in the last couple years, the only downtime of my site was
a) my own fault for fubaring something (technically that's not DH downtime)
b) planned downtime announced by DH. And THAT has been very, very infrequent.
Schweb makes a very valid point. You rarely hear people posting about how great something is, only when something doesn't work or is of poor quality.
Just look through MacForums. You'll see a plethora of people posting about how their Macs don't work or some other issue. How many threads are people praising how great their Macs are? One? Maybe two?
This doesn't prove that Macs suck, it just goes to show that some people have issues with the product and are trying to get help. These people only signify a small percentage of total Mac users. Thus, the vast majority of people are quite happy with their Macs.
The same applies for any other product/service. If a small number of people are complaining about Dreamhost service and yet the service is doing well, then it is safe to assume the vast majority of Dreamhost customers are happy with their service.
So like Schweb said, take all complaints with a grain of salt. Sure, they are legitimate complaints, but it doesn't mean EVERYONE is having problems.