Things are generally slower this way, for sure. Part of the problem is that, in order to keep things simple for newbies and to disturb as little as possible on the tablet, we're running Debian in (1) a "virtual" chroot filesystem that (2) lives in a mounted image file on a (3) flash memory card with fairly slow read/write speed. If you run an alternate window manager like IceWM, then you're also running (4) a nested X-Server (so, TWO X-Servers) and (5) TWO window managers.

The first thing that will really help your Debian speed is to use the alternate window manager only when you need it. Use the Debian chroot terminal and Synaptic from within OS2008.

There is a noticeable speed improvement if you set up your chroot in its own partition or a folder in your rootfs (if you have a big primary partition). There would probably be another big speed improvement if you were willing to shut down the OS2008 system like penguinbait does with KDE (or like fatalsaint suggests above). But one of the big plusses of this system is that you can keep OS2008 open and run another window manager at the same time, and you can switch back and forth.

I'm working on a new version that will help with this kind of disappointment. For example, my next version will run Kazehakase (or similar) as the default browser, rather than Firefox. Firefox is really just unacceptably slow, and I really shake my head when I think that the whole point of FF was to strip away all the bloat of Netscape / Mozilla. It has ended up being big and bloated again...

There are some optimization tips in the Debian chroot thread. More are always welcome.