Infinite possibilities only if you knew how to harness it. There's lots of people who complain how crap their phone/device is but ironically there's also people who buy phone/device that doesn't even know how to make the most out of it.

First of all N900 is not a phone/smartphone. It is an internet tablet with phone capability, so to pit N900 against other smartphones you'll see N900 failing quite quickly due to its flakyness to act as a proper smartphone. You would have also noticed that N900 is part of the Nokia Internet Tablet family and that N900 is the _only_ Internet Tablet with phone functionality.

To say Linux OS is useless shows how stupid you are on the contrary. Linux is not an OS, its a kernel which is the heart of what it is a part of the OS. Linux kernel is usually combined with many userland tools to effectively make it what is properly known as a distribution. Many wintards like you simply dub it as Linux OS when its more complicated than just that, in fact I dare you to call BSD an OS as well, that'll stir up BSD users when they have variations known as flavour.

Now to actually give you reasons why N900 is better than other smartphones (and again for people like you who keep saying its a smartphone when it isn't I'll dumb it right down):

• It has a FM transmitter built-in. No other smartphones has that as standard.
• You can multiboot with other distributions/platforms as long as there's people whom have ported some of the core functionality of the device. This fundamentally goes into how somewhat portions of the device's source code is available in the public domain, without those portions of the device's source code and with people wanting to put other distributions/platforms on the device would be awkward. Have a look at iphonelinux project for instance, and then note how there's only two android phones that actually has factory unlocked bootloader which allows one to install OS of their choice, the rest of the android phones on the other hand needs hacking.
• The whole maemo directly interacts with the hardware like what you would expect linux or any other OS to do on a regular computers/laptops/phones. Android on the other hand runs Dalvik VM which is virtualisation on top of the linux kernel. Direct interaction gives less overhead when it comes to I/O performance, smaller memory footprint and as a result generally faster response.
• It comes with by default 32GB of eMMC space with expandability option via microSD. Hardly any other device would actually be generous to offer 32GB internal space _plus_ storage expansion via microSD in the form of what you want to dub it as a smartphone.
• Because of maemo doesn't run on VM and it has a linux kernel with an open source wireless driver. There are wireless penetration testing tools made for linux and specifically due to the nature of the setup. Running wireless penetration testing tools such as aircrack-ng on N900 is almost as effective as running aircrack-ng on a mobile computer that has proper linux driver support and runs linux. In short, N900 is a godsend in some ways for professional wireless penetration testers whom wants to do auditing on businesses that pays them to do so. Try finding equivalent of this on any current smartphones.

Apart from Nokia N900's shortcomings with various issues, overall it remains to be a tinkerer's choice for handheld device alongside openmoko for instance.

On a final note, linux appears on almost every device we all own, its also utilised on various servers and supercomputers around the world. Unless you're living in a third world country, despising linux shows how conceited you are.