Seems the discussion has pretty much turned to the Nokia, but I thought I'd still toss in my 2 cents...
While I haven't used the Nokia, I cannot offer a viable opinion except that a) it's going to be a lot heavier & larger than the Touch, b) it will probably run hotter, and c) it's battery life won't match the Touch either (though it's been suggested that you can buy a few extra batteries and swap out when low). If you're looking for the sheer number of file formats, you can't go wrong with the Nokia, after all, it is a full-fledged, though slightly neutered laptop.
On the other had, you can do pretty much whatever you like on the Touch provided you can find the source and compile it. There have been a ton of apps made for the Touch since even before the App Store, so development will continue on both sides of the fence. You mentioned an App for viewing files etc. on the Touch, I use an App call "Files" that IMO is the best bar-none. I've used several PDF viewers but the one in Files lets you place bookmarks, remembers where you left off, switches portrait to landscape and is pretty well done. It also allows you to view DOC, PPT, XLS, RTF, HTML, etc. There is also a comic viewer available that lets you view comics in cbz or cbr archive formats (one of them even has a page change feature where you tilt left or right to go back or forward in the book. Stanza supports LIT, Kindle, Mobi, PalmDoc, RTF, DOC, etc., though they have to be DRM-free. It will soon to be available for Windows systems, but already works with Mac.
The Touch is also your entertainment system when you're not reading; i.e., videos/music that remember where you left off (good for audiobooks, movies, and podcasts) and there are a ton of games on it that are ideal for a few minutes at a time. The PIM features of the Touch will sync with you PC's PIM software; i.e., Outlook, so you don't have to worry about keeping things sync'd between multiple PC's/laptops.
Ultimately, I like the Touch for it's small, portable size. I can, and do, carry it with me everywhere and use it all the time, not just for reading. A new version was just announced that has improved battery life, a brighter screen (not sure about this, but some people are reporting this), added speaker, integrated Nike+ (if you need it, I'm not sold yet), hard-key volume control, and the support for the new headphones with the built-in mic; it was actually just awarded CNet's Editors Choice Award.
Lastly, don't forget about instant-on as opposed to waiting for the Nokia, or other Internet Tablet/UMPC, to boot.