@pmcd: Yes, it does have a small fan, on the side. The device is always shown standing upright, but i put mine on the side with the fan facing up. The exhaust usually is out the top so that is now exhausting out the side. Seems to still work perfectly, and i have never heard the fan spin to full speed, even during the most detailed HD videos on full fast forward. The Addons questions is more of an OpenElec thing, and this if my first go-round with OpenElec, and it looks like all addons which work with XBMC normally will work with OpenElec, but don't quote me on that since i haven't tried all of them, and i am not on the OpenElec dev team.
@ NeilF: Turning a computer on from a fully off state is not necessarily unique to this device, there are a few stars which have to align to make it work; 1) motherboard must have a always on USB header, or IR sensor, 2) you must have a remote which has a power button, 3) you have to make sure you configure the mobo and remote to work correctly together to get what you want. All of that is why i'd rather buy a system which has onboard IR or at least an IR sensor on the front of the machine instead of buying a dongle, which has a remote with a power button. It just makes it a lot easier. However, i was burned with a previous D525 system which had that because the remote wasn't a full MCE remote so a lot of the buttons didn't work with XBMC. But the Xtreamer works perfectly. I do have a Monster (Harmony) remote which i haven't set up yet for this since the remote is very useable right out of the box. I have only re-configured a few of the buttons to give myself some of the extra features that XBMC allows, i can provide the modified keymap.xml, and the remote xml files if needed to enable those features. However, the remote is very useable which is why i haven't wanted to spend the time to configure the harmony yet.
To answer your questions:
1) Correct. That is exactly what i did. However, it did come with a European power cord which goes to the external power brick, but i had a compatible cord so that was an easy switch. That is also a reason to wait until it is available on Amazon if you're in the US. I pulled it out of the box, connected it to HDMI to my TV, connected power and ethernet, then hit the power button on the remote, and 10 seconds later i was looking at the XBMC home screen. Perfect out of box solution.
2) That is what their site says, i do not have a 3D tv, or any 3D video files (personally i think 3D is overrated, but that's my own opinion)
3) There are scrapers built into XBMC which will index all your connected shares and grab the information from those scrapers to get cover art, and all related information. All you have to do is Add Source in each of the sections (Video, Audio, Photos, etc.) then it will ask you if you want it to scan the source and which scrapers to use. Pretty easy if your stuff is named correctly, or in correctly named folders. I have only seen 1 movie (or was it a TV show, i forget) so far which was cataloged as something else, but no big deal.
It's REALLY easy to use if you've used XBMC before, and it is easy to use for basic functionality for anyone new to the application.
Let me know if you have any more questions, i'll try my best to answer, or i can test stuff out if needed too.