64bit Linux finally happened for me.
There were a few stumbling blocks, most of which involved the general hesitation I had with stepping away from so much software I was relying on. But now that I've seen how trivial recompiling is, and most especially because Macromedia Adobe Flash has an alpha out for Linux.
Yeah, an alpha. But I couldn't tell. Way back when, there were 32bit betas which were horrific.
Software > Internet >
Downloader, BitTorrent, RSS, video player etc. I don't even know how to categorize this..
more possibly coming later
Software > Bundled Server Software >
I would NEVER EVER recommend regular humans go anywhere near running raw server software on their desktop. It's a horror - I mean truly a horror unlike any you've ever imagined - to get that shit to work, to lock it down and to keep it running. If for some reason you did want to run a server, use a proper server distribution. A branch will eventually crop up for Unity Linux I'm sure, but there are Linux and BSD distributions which excel at this task.
So for us regular humans, a LAMP (software bundle) is the best thing to use. This is a collection of all the necessary tools which have been pre-configured to cooperate and bundled together in one .. much easier to use package. This concept has become wildly improved over the years, and I've used a bunch of different packages.