As for "tme it takes DH to activate a shell account":
I've never found it to be completely predictable. When things are going well, it seems almost instantaneous (last night around 0200 PDT) it was a matter of minutes for me, but I've had it take from several hours to a whole day. Anecdotally, for me it is usually within an hour or so.
What does sometimes take way to long to "activate" on Dreamhost in my experience, are mailboxes.
On a somewhat related topic, sometimes the speed with which Dreamhost does stuff via the panel is almost instantaneous. Early this morning I created a new domain, pointed Network S*lutio*ns registrar data to the Dreamhost servers, and was propagated and surfing the site from the west coast wall in a single 30 minute period. Very Cool!
It would sure be nice if it always worked that way.