And within not that long you're tinkering away and learing loads about Linux, from the kernel upwards. Can you even run perl or a webserver on another device sold as a phone? And you can write and run <language> programmes on device. It's great.

Concept: "3.5inch 3G tablet computer," and all that that brings to mind.
Caveat: released 2.5yrs ago so some modern harware is better or faster. Therefore, in some cases software demands are greater than its embedded capabilites (flash and embedded videos are a sore point).

One other advantage that implied by Linux is that it provides raw access to most of the phone's hardware. A good example of this, in terms of customisation, is how the camera functionality has developed over two years.

When I first got the phone, you opened the lens cover, you got the camera and that was that. Then, somebody wrote a Flashlight application (using raw access to the LEDs), but it was a pain to switch it from the status menu after opening the lens cover. Then QR codes happened, and others started work on mBarcode, which added QR capabilities to a phone that was never designed for them. Hmm, our camera's getting pretty useful. Not to mention FrontView, which can scan a document tolerably well from a photograph. So, someone wrote a "camera lens launcher", that waits for the opening of the camera lens and offers up a menu, all I now have to do is open the camera lens and I can select camera, flashlight, QR reader or document scanner. Oh, and a whole new camera UI has been developed and released as part of the CSSU. If you want to talk customisability, the camera functionality is one to look at, because it's been pretty much completely replaced since Nokia released the phone.

Obviously, this is just one example and the guys who've been working on USB host mode, kernel-power or CSSU might be feeling a bit overlooked - it's all but impossible to cover the whole subject. However, if you're looking to do a presentation of some sort, camera functionality might be one good focus.