Then I think you may have bought the wrong gadget. The N800 is made by NOKIA, so they kind of expect you to have a "proper" cellphone, preferably 3G. Personally, I would not have bothered getting the n800 before I got an affordable data plan.
Cellphones with PIM have killed the PDA market. You should be syncing your mac with your phone, which is with you all the time. Sure, I'd like to sync the N800 too, but the phone is more important.
The beauty of the N800 is "internet everywhere". Its an internet tablet. At home or office, where you have a proper computer, why use the n800?
Sure you can use it as a media player, but there are better solutions out there.

Lots of pixels, screen needs to be small. Therefore it needs to be held close, about 20cm/8". Eventually we all need reading glasses.

The keyboard is just for big trips, or the odd occasion tyou know you'll need it. Other times you can choose finger, stylus, or writing recognition. The latter especially is very fast with a little practice.
It sounds like the iTouch would have suited you better. Its a beautiful media player, but lack of bluetooth for cellphone access killed it for me. The iTouch is a usable PIM and has good email, once its jailbroken.

Instead of the Eeepc, consider a second-hand mini-laptop. I got an old IBM X-23 to take on vacation for movies and web. Cheaper than an Eeepc, and with a proper screen. 1.6kg.