My rPi arrioved last Wednesday. I can't say that I had a real application for it in mind. It was more of "let's see what this thing can do and go from there". I found an old 8GB SD card, a USB keyboard and mouse, an HDMI cable and an HDMI/DVI adapter to plug into a monitor and started playing.
I first loaded raspian onto it to try things out. I was a bit disappointed but not entirely surprised with how slow it was just loading a web page. From there I moved onto Raspbmc. The UI was sluggish compared to my Atom HTPC but video playback (including HD) was flawless.
I bought a new 16GB SD card and reloaded Raspbmc on it and that's when my problems started. Scraping was glacially slow. And after a few hours the rPi would often go to a black screen and I'd have to pull the plug. Sometimes when I reapplied the power nothing would happen. Then I discovered that the XBMC database files were being corrupted. After trying to recover from that a few times I was a bit discouraged.
I finally turned on debug logging in XBMC and noticed continuous CEC polling timeouts. That made sense; since the monitor didn't have an HDMI plug it certainly didn't know about CEC. I turned that off and the scraping performance improved. Dramatically! But I was still getting database corruption and decided to go back to the original 8GB card. rPi has a long list of reported compatible and incompatible hardware and the 16GB card I was using had been reported to be both compatible and incompatible.
With CEC turned off Raspbmc on the 8GB SD card seems quite stable and not nearly as slow as it was with CEC turned on. It's not a speed demon by any stretch; I don't have a huge library (a few hundreds of items, not thousands) and it's taken 14 hours so far to do the original library update. I expect it'll take several more hours before its done. Once that's done I'm going to use it for awhile as a secondary HTPC and see how that goes. Now that I've got the CEC issue out of the way and seem to have an SD card that the rPi is happy with, I'm hopeful.
The CPU temperature is stable around 55C, and that's with being run continuously at close to 100% CPU usage since last evening. That's quite good. Overall I'm extremely impressed with the rPi. I've had the expected teething problems that are associated with just plunging in and seeing what happens, but other than that it's been exceptionally trouble free. The SD card compatibility issue is a bit of a concern, especially since it appears that a card can *mostly* work and only manifest problems that can be mistaken for application errors. But once you've got a working card it's rock solid.
The next question is, what with I do with my *second* rPi?