I have to say try OS 3.0 for now and imagine it runner on a faster processor and with multitasking. It will be around in June. Personally I am between it and the Pre but going more for the Pre.
Safari has been stable in FW 2.2 it pretty much never crashed, but yesterday in OS 3.0 beta 5 crashed on me. The other betas did not crash on me.
I don't know but attachment support beats Nokia to the curb, even the old one OS 2.2 in Exchange was good. The attachments are right there on the bottom you just touch it and it just works. I use callwave as my VM provider so every voice mail I get I have to listen though e-mail as an attachment. having used both S60 (you need to go to options -> attachments -> download attachment -> and then click again to play the attachment) and iPhone, I found the iPhone to be much faster in that just one swipe to the bottom and click - the message plays.
Overall, I won't deny the slowness of this phone. It is slow, but at least it does not draw a page until it is ready for your input. The 5800 will draw the page but when you click it won't respond until it is done. If you compare both side by side you will see this. That having been said the 5800 is generally E71 fast in most things but it takes a while to load and also be ready for your input. I fully expect that a company like Apple using the Pre as a benchmark will get about 80% there with issues like speed and multitasking with the new hardware.
The truth as you say it is slow, but it is also very consistent. So even if I know I need to wait I know that I will get the result I want if I wait. If I try to rush things it is annoying because it is slow without a doubt, but still I will get what I want. With the 5800 IME, if you rush things on it or you go too fast for it, it will get confused and you will end up in a menu or setting you didn't expect.
For me personally, I am betting on the Pre without knowing anything but watching the nearly 45 minute video they released of it recently.
Anyway, I think either the new iPhone, or the Pre, or the Samsung l7500 are better bets than this. Rather I would try any of them first in my situation before trying the N97. Again that's just me.