Still can't post in the 5800 thread, so I'll post here instead.
I'm seriously considering canceling my N96 preorder (it's released on Oct 15th in Sweden) in favor of the 5800, for a number of reasons.
5800 advantages (compared to the N96)
1) It only costs a bit over half as much as the N96.
2) The N96 has received lukewarm reviews, and may not sell very well. I fear it might go the same way as my current phone, the N93. That is, abandoned by Nokia a few months after release. The 5800, on the other hand, is the first in a new line of devices - this line is likely to get a lot of attention from Nokia for a while.
3) Higher screen resolution, and bigger screen (I think I read 3.2 inches, as compared to the N96's 2.8 inches). I'm sure this will be nice for movies and photos.
4) In the case of the 5800, I won't be paying for a DVB-H receiver (mobile TV) which I can't use since there are no broadcasts in Sweden.
N96 advantages (compared to the 5800)
1) 16 GB built-in storage. The 5800 only has a card slot (although, a 8 GB card is included when you buy the phone).
2) The N96 has more software available for it than the 5800 will, because it will take developers some time to make the needed adjustments. For example, it'll probably be a while before Python (PyS60) is released for the 5800.
3) The N96 has N-Gage, which me and my N93 have been waiting for, for over 2 years now (grumble). Because of the lack of hardware buttons and the new 360x640 screen resolution, it may be a while (if at all) before the 5800 gets N-Gage.
I think the 5800 will sell pretty well. I think a lot of people have been waiting for "a cheaper iPhone". And I think people will appreciate the fact that it has a semi-familiar S60-interface.