I noticed that the OP asked about NNTP news readers while the (only) response was about the RSS news reader.. not quite the same thing!

I haven't seen any NNTP reader for the N800 (although one could be hidden inside one of the bigger 3party multi-function apps for all I know), but if the demand is there there are several that could be ported. Maybe 'pan', which is a gtk2-based reader: I haven't looked at it, but gtk2 is what N800 uses.

I own several PDAs. What I like best with my N800 compared to the PDAs are battery- and screen related:
1) The N800 screen is just much better.
2) Except in sunlight.. My Palm T3, for example, has a transflective screen, which means it suddenly gets readable if it's put in direct sunlight. The N800 doesn't have a transflective screen, i.e. indoor is best (and stick to the shadows outdoor)
3) The N800 can stay on wi-fi all day and more, and the connection is alive too.. I get my emails, google talk chats etc. coming in. None of my PDAs can do anything even close - they simply can't be used that way. Maybe the smartphone-PDA devices with wi-fi is better in this respect, but I don't own one of those.
4) I have to keep remembering to charge my PDAs every few days, if I forget they lose all information. Doesn't happen with the N800, you don't lose anything even if you remove the battery. For PDAs you would need non-volatile memory to do the same (e.g. newer Palm and Treos, or some smartphones). I'm constantly running a backup program on my T3 just in case I get a hard reset or a battery runout, and I've still managed to lose important information. With the N800 I can be much more relaxed.
5) The calendar, and some of the other PIMs on my T3 is better than what I can use on the N800. The PDA is a better PDA, the N800 is an excellent internet device. Slightly different beasts.