I have been testing several types of mobile devices, including Psion way back in the past, Palm (from Palm), Palm (from Sony), Windows Mobile devices and Nokia Symbian based devices. My most stupid acquisition by far was an UMPC (Asus R2H) : battery life was miserable, system getting very hot, sluggish CPU, etc. One of my favorite acquisition is the N810 : solid hardware, beautiful machine, very manageable battery life (in fact, I barely turn my N810 off), and indeed a growing list of applications and very good support and hints from this forum.

I wouldn't try to compare with an iPhone. This is not the same market. iPhone looks very nice but the whole mentality behind (everything is locked down, can only be used with iTunes, extremely expensive accessories, ...) is just way too bad. Now, if you have a serious look in the iPhone AppStore, you won't find that many usefull applications. There are a lot of gadgets, really.

On the other hand, I'm really keeping a close eye on what's happening with Android. I'm convinced this is going to create a big "kaboom" on the mobile market, not only from a device (hardware) perspective, but definitely by the way we are going to use and leverage such cloud computing entry points. If you don't know too much about Android, try to find the July issue of Wired magazine, they have a pretty neat article about it. As Android is open source, I'm even quite sure there will be always someone somewhere being able to port it for the N810, provided Nokia can open up full docs etc on leveraging the N810 hardware.

So, should you go for a N810 ? I couldn't tell, because you haven't mentionned what you were looking for and what you intended to do with it. THAT is the main question.