Wow! That is a heavy collection... I mean, all top end Symbian smart phones. Nice.
I recently went from the N95-4 to the 5800. The 5800 is noticeably thinner and lighter, and faster. Its size and simple, uncluttered looks give the impression that it's just a basic handset. However, once you unlock it and its screen lights up, its relatively large, high res. display and powerful OS and apps make you realize that this is very capable symbian smartphone... I love this little thing. Anyway, my point is that for you, coming from such large and feature rich handsets, it might take some getting used to.
I have an N800, like your N810. The 5800 could have really benefited from having a direction pad and a back button. I have a feeling one of the next touch screen handsets released by Nokia will be something like the
7710, with a d-pad. The reason I mention this is that, for example, scrolling through a long Web page on the 5800 can be cumbersome since there isn't an on-screen scroll bar for you to drag; instead you need to drag the page little by little - maybe I'm missing a hidden feature, but I haven't been able to find another method. The point is that the N8x0 internet tablets, with their larger and higher res. displays and dedicated buttons, and better support for multiple browser windows, etc provide a better Web browsing experience.
It comes does to this... if you want a small, all-in-one handset, that does not do everything quite as well as its larger predecessors, but is still quite impressive, then the 5800 might be for you.