I love my PB as it is now. except for the too less num of mail/chat/reader apps.
In case you are adventurous, QT is available for playbook.
FBReader/Coolreader can be made to work with QT.
I have a "very stable" vanilla port of native FBReader working on the PB (1.x fw), but am not very confident of releasing it to others. (By that i mean am lazy to start trying to fix bugs etc.,
Everything in fbreader works beautifully; issues are that the toolbar is always visible and the setup dialog is very ugly to manipulate. People who have used Iliad would realize what i mean. And the pkg is about 80+mb as i just threw in all qt stuff into the bar file(again lazy).
Coolreader is a little more unstable so i dropped it.
This maybe a mute point if OS2 comes out as Android provides a lot of reader apps.
But knowing android, i am sure there will be issues with battery life and performance.