Dreamhost DOES NOT install ZP into user's directory when doing the one-click, that's how they do updates but most likely major: 1.1.5 to 1.1.6 to 1.1.7; not nightly builds. All files reside on their servers. So, if you want to keep current, do-it-yourself. It's easy, especially compared to some of those others offered by DH.
I created a new subdirectory but used all the info DH creates when they do the install: the SQL db, the password, etc.