yeah the N800 is a great piece of hardware.
If you don't really need extra space, you don't have to clone anything.
80MB of free space is more than plenty
I suggest that you try liqbase (really cool app) and Tear (a faster browser) and few others:
*Garnet VM is also interesting for mobipocket ebooks.(it's a palm emulator)
*Kchmviewer for chm files.
*Easy Debian if you like to have a full debian chroot .. (pretty amazing)

If you use fbreader all the time, I'm sure you will find calibre (a desktop application for PC/Mac) really useful for converting ebooks. mobiddrm may even help you

Otherwise, enjoy your N800 ;-)