That's a hard one to answer, and it is also a consideration even if you upgrade it "manually". Having upgrade several sites, my experience has been mixed.
It depends a lot on what you have installed, and what modifications you have made.It is also possible some of your components will "break" with the security enhancements included in the upgrade. This can't be avoided if you wish to keep your site from being cracked; you will have to wait for/lobby the component authors to upgrade the component, and then install those upgrades.
I think the important thing here is that, with the Dreamhost "one-click" upgrades, if you don't like the changes, you can simply delete the install directory and rename the DH provided ".old" directory as apporipriate (or delete files/subdirectories and copy the contents of ".old", etc.) and you are back to where you were - no harm no foul.