Congrats! Can I ask a few ?s
1. How well dose it work (and flaws or bugs?)
2.How hard was it to do?
I've already had a Mac mini hooked up to my TV for about 6 months, using Front Row as an AppleTV. Getting AppleTV to replace Front Row was just as simple as following this tutorial. The advantages? Check out the screen shot below from my main PowerMac G5's iTunes:
By directing the root-level "Media" folder via symlink to an external 500GB USB drive, I have effectively turned my mini into a giant AppleTV, but with easy access to modify it remotely by VNC, AFP drive sharing, or even SSH. With the added plugins "ATVFiles" which allow playing of non-iTunes compatible media (ie MPEG2, AVI, etc), and the "Exit" plugin, this setup is much friendlier and more elegant than Front Row. The family understands the interface a little better, and the kids are much less likely to accidentally "MENU" themselves out onto the OS desktop. Less need for a keyboard and mouse in the living room.
When the AppleTV software is running, my PowerMac sees it as a genuine hardware device. I can much more easily manage my content from my main computer, selectively choosing what is sync'ed (with 500GB I've chosen everything

). So I've got 150-some odd movies Handbrake'd in and a few dozen episodes of ripped and/or iTMS purchased TV shows. This conveniently creates a remote backup of all my media simultaneously (though the Media folder directory structure and file naming conventions are rather cryptic, all the files are there if needed). Unlike Front Row and other iTunes sharing, the AppleTV software also correctly updates play counts and last played on the mothership which is great for my smart playlists.
FWIW, I also successfully created a separate boot partition that turns the Mac mini into a pure AppleTV, but I found it to have much less customizability this way.
PS - one more advantage...I have an old-fashioned 4x3 Sony Wega with only RCA inputs...the Mac mini DVI-->Video adapter works perfectly. From what I understand, the AppleTV would not easily interface with my TV.