I've only been with Dreamhost since January 2007 but i've never been disappointed by them!
I'm still hosted with them and i don't intend to move unless all my websites are being kicked off the net!
When it comes to customer service i'd give them a 10/10. Their respond time is sometimes almost immediate, as in less than 5 minutes after you contact them. Their staff are knowledgable and helpful. The longest i've had to wait for a response was 30 minutes.
When it comes to their reliability, i'd give them 9/10. My sites have only ever been down once, and they contacted me weeks before to let me know that their will be a short outage while they upgrade the server that my sites are on.
As for services, its an 8/10, you have so many options on a shared hosting that you'd want to ask what is the point of getting dedicted or a VPS. You can install almost any server software you want from SSH and you have full control of your server environment from a .htaccess file. The only draw back is you don't get sudo, but then thats a good thing because that means you can't break anything beyond repair.
Their wiki offers extensive help and information on installing all sorts of software, and to top if off they offer a one click install service, which basically allows you to install some very common software with the push of one button like wordpress.
Like i said i've only been with them since 2007 but my bandwidth and the amount of space i have grows each week. So it just grows with my website, I'll never need more bandwidth and if i do i believe its only $1 per gig. My total allowed bandwidth should be hitting TB by now.
They have all sorts of plans and payment terms, there is monthly, yearly, every two years, every 3 years i believe every five years and every ten years, i might even be missing a few but they offer you so many things at such a decent price its hard to keep up with all the things they're giving you. A 10/10 for the range of things they provide for such a small price.
I believe their specialty or main focus is on shared hosting and thats what i've got and my server has never dragged, except once before the did the upgrade but since then the speed has been incomparable to any host i've been with. A 9/10 for server speed.
If there is anything i would say i don't like about dreamhost service is the limit that they have on sending out emails. They cap your emails so you can only send a certain amount per hour, can't remember how much it is off the top of my head but their justification of why they've done it is satisfying. Its simply to reduce the amount of spamming and hence when emails are sent from their servers the don;t end up in hotmail junk folders. Even though it may not be your site that sent spam e-mails hotmail will chuck your messages into the junk folder and from what i can remember thats why they've capped the email. On the bright side of that they offer pop3 and smtp and you decide where to access your emails eg. mail.domain.com or mychoice.domain.com; A 6/10 for email.
I'd definately recommend Dreamhost to anyone looking for a good reliable host who pride themself on true customer service, putting you before everything else. An overall rating i'd say of 9/10 for Dreamhost.