Judging by the reply you got, it sounds like the support rep thought you meant pointing to the DH nameserver by the IP address, instead of the ns1.dreamhost.com address. The thing about doing that is no, they don't *always* tell you if your IP address changes, so that's something you have to kind of keep an eye on. So, if you were to enable subversion on your site, sticking with that example, your IP may (not necessarily will) change, because not all servers are set up for subversion. Or that's how it was when I set mine up–it could have changed by now. Basicly, the only time they tell you you're changing servers, in my experience anyway, is if they need to move you to a different server because either yours is crapping out, being unresponsive, or they feel your site is the cause of certain server issues. This falls under the same category as their recommendation that people who have a unique IP address attached to a domain name should still prefer to give out the domain name, rather than the IP address, because it can, and sometimes does, have to change.
Yes, I have an opinion.
Get a minimum 50% off with the "haveadreamyday" promo code, and... have a dreamy day. Original, no?