I nearly bought an android phone last year but didn't (phew!).

What swayed my decision to buy the n900 was:
(a) It runs linux and is mainly open-source. If Nokia turns round and says "f*** you we consider your n900 obsolete and thanks for the money" then it would be well-supported by the community and means software will always be available for it. Even write my own software.

(b) I needed a tv-out function. It's great for watching tv shows and movies. I don't even need to recode the video files.

(c) Physical keyboards are a must for a device to be considered a "pocket computer" - gives you more flexibility feature-wise.

(d) When I browsed through applications for the n8x0 series was impressed by the lack of "pull my finger" & "I am rich" apps. Instead I found applcations that seemed genuinely useful.

(e) I can use my wii remote to play games via emulators. Highly entertaining. You can also play Quake - I like Quake almost as much as I like cake. Of course you can play it via tv-output too.

(f) The browser is much better than other devices - it's the closest you get to browsing on desktop/laptop computer.

I'm very happy with my n900 and is one of the few successful decisions I made in my life ( unlike a career as a software developer!).

Things to consider about n900:
(a) It's not full-featured phone - most other mobile phones are far superior in this respect. In fact it is very basic but for me reliable and does the job.

(b) Camera is a bit weak and flash is as useful as a burnt-out matchstick - great photos in daylight though. My SE k800 was far better (only 3.2 megapixels)

(c) USB OTG host mode does not work at all - you cannot plug peripherals into the n900 - you could with n770 & n8*0 models.

(d) Use of bluetooth keyboards & mice is woefully inadequate and virtually non-functioning. It would almost be a "proper" computer plugged into a tv !

(e) There is no sign of the free version of OVI maps coming to the n900. I think most of Nokia's other devices have got it. Not a show-stopper for me but a little disappointed though.

(f) There are a few whiney people in the forums at the moment (Who should ideally wander the streets holding a "Jesus will save you" placard and chanting "we are all doomed") some make do make good points but some moan about "My n900 stops working when submerged in boiling water" type rants. It is a great community and do enjoy myself here making sarcastic comments like this.
Apart from that everything is ok.

I consider iPhones and Android phones to be more "entertainment" devices with regards to the available applications. That's fine and people I know have bought them and are very happy.
The n900 for me is more of a "work"/hacky type phone and that is appealing to me. Many of the applications are actually useful (e.g. vncviewer, moobox, msaber)

The above points were in my mind when I chose the n900 in December 2009 and was exactly what I was looking for.

Really think about why you need a device like this before you commit to buy it. It's a lot of money but if it fits your needs well worth buying.

I've never seen that. 3rd party software? Faulty phone?