I have a raspberry pi for quite some time now. I tried only a few things till now, but it is great. I used it about a few hundred hours for video playback in FullHD using raspbmc which is a XBMC port.
It works so great and is amazing. With all the addons available it got better and faster than any smart-tv I saw so far.
The best thing the installation was is so easy. You simply download this file:
http://download.raspbmc.com/downloads/bin/ramdistribution/installer.img.gzdecrunch it and (on MorphOS) copy the around 80MB it over to SD card in card reader using RAWDISK: device. I guess there is something similar to "dd" images to disk in OS4.
Thats all it needs. Just put back the SD card into the pi and it will download and install without any further user action. After around 10-15 minutes you have a proper and fast xbmc on your pi and anything can be configured by using cursor keys, return, c and ESC keys. Of course the mouse is supported, but I never used it.
I used some wireless keyboard with joystick mouse build in as remote. A full keyboard is quite nice, as you can jump to a specific file starting with a g using shift-g for example.
Raspbmc can handle nfs, smb and all other stuff needed to connect to servers and NAS systems, so you can stream from your NAS, Amiga or whatever without the need to copy anything onto the pi itself. It plays 1080P without any problems.
In fact it also creates a better picture on cheap tvs, as it scales on the pi to nativ television. Thats why I stream my recordings from hdd recorder to avoid the cheap telly activates his crappy scaler.
It plays nearly everything out of the box. Even raw satelite transponder files recorded by most hdd recorders. These contain non a/v related packages (epg, teletext, ...) which sometimes fail with other decoders. The pi does fine.
However to decode mp2 and wmv you need to order a licence as the raspberry foundation did not do that for a simple reason. It is ment for school and all recent codecs like h264 are available. The licence gets tied to your hardware. The price is 2$/3$ each, so not that hard, but compared to the price of the pi itself around 1/10 so its fine to keep hardware cheap in generel.
Before I forget. You can of course connect a digital tv box to the usb port of the pi and you will get a fully featured hd recording system. Isn´t that great?
USB Stick can be connected at runtime and the drive gets available automatically, so you can play and data located on that drive, too.
Addons like YouTube and media archives are available and so much fun. The YouTube thingy is the best I have seen so far. In combination with a keyboard its simply fun to search and watch all the stuff available.
And just remember only around 50 bugs (inclusing cable, powersupply and SD card) for it.
Speaking of SD card. Make sure you get a fast one. The size does not matter. Most stuff wll work with a 2GB card, but if the card is slow, then it makes no fun as you wait for loading a lot. Get at least a class 10 card to be happy. Just remember if you don´t plan to store any movies on the card, which I recommend, then get 2-8 GB cards. I was lucky to get a class 6 set (2x 16GB ySD + 2 ySD -> SD adapters) for 16 Euro, marked as class 6, which is hell faster than that. A Class 6 Sandisk is slow compared to that no fun.
Speaking about a desktop OS, especally the latest 512MB RAM version is great. I tried with the 256MB version before and it was fast and responsive. For usaually work like writing a letter or surfing the net quite nice for a cheap system like that.
Hope it gave you a little inspiration.
Geit