After posting that, I decided, wotthehell, I'd gone that far, I might as well finish the job before I installed any programs. So I did the WM6 upgrade, then installed Mobipocket. I can't say that it seems any faster to me, but maybe for what I'm doing, I wouldn't notice the difference anyway.
Now I guess I should put eReader and Adobe and whatnot on it, and try out those epub readers. And then stop the neepery and start enjoying reading again.
