I't's going to be all about space management to some degree. If you're selective about how much music and video you put on it at any given time, and you don't load it up with every single free app available in the app store, you should be fine. I'm not an app collector, but I do have quite a few. LOTS of those, I don't bother to sync to my iPhone. I just don't use them. Some are free games that I don't play much. Sometimes I'll switch out one game for another depending on my mood that week. If I put all my apps on my phone, I'd overrun the memory just with those.
iPad specific apps are going to be proportionally bigger because of the resources needed to support the larger screen. Bigger screen means bigger bitmaps for backgrounds, etc. Not all will be larger, but enough to make a difference. Manager your apps!
Documents for iWork shouldn't be an issue. I've commented elsewhere on here that the 2500+ word processor, spreadsheet, presentation & PDF documents I use regularly for work fit in well under 2GB. I doubt too many people will by trying to carry that much crap around on their iPad. even I don't intend to use it as a total laptop replacement, though it will be nice to have enough room to carry those documents for reference should I need them.