CrackBerry and BlackBerryOS are reporting a leaked OS 18.104.22.1688 for the BlackBerry Curve 8520. RIM have said that it won’t be longer than 2010 before we start seeing OS 5 rolled out across a larger gamut of devices so it shouldn’t be long until this is official. So if you want it now, and you’re okay with some third party apps not working, then go ahead and give it a try. Usual caveats apply.
If you’re getting the error “File Temporarily Unavailable”, all you have to do is keep refreshing the screen. It took me about 15 refreshes to finally get the download to work.