Mavericks installed on my relic. It's awesome!
Installed it on my mid-2007 15" Macbook Pro. The trackpad has a separate button!
Runs like a dream so far, everything is so much smoother. Hasn't been this good since Snow Leopard.
Been through 6 operating systems: Tiger, Leopard, Snow Leopard, Lion, Mountain Lion, Mavericks.
Only modification was adding 4Gb of RAM, it came with 2. Some phones are probably more powerful than this.
Going strong after 6 years, still running the latest version of OS X.