Automatic reference counting dates back to probably the 1950s. If it "works just as well" as garbage collection, don't you think it would have won by now?
That said, I think reference counting warrants more attention than it has gotten in memory management research. If you're willing to punt on the leaking cycles issue, you can get a lot of mileage out of using a reference counting collector as a tenured generation with a copying nursery.
Are there implementations one can play with?
Important: Garbage collection is deprecated in OS X v10.8. You should use ARC
instead—see Transitioning to ARC Release Notes.
Whether ARC is better or worse than GC overall is immaterial. Apple has moved away from garbage collected Objective C.
... In Apple's Sandbox. Apple has also killed ethernet and other very not-dead in the real world things.
They did remove it from their line of portables as most people use wireless with their laptops (and they scored some valuable real-estate on the main board!) but you can get a Thunderbolt network card if you really want to be tethered to your desk.
Apple's computers (desktops included, save for the Mac Pro which is essentially EOL) no longer have an optical drive, maybe I should have used that instead. I saw a coworker hunting for his MacBook's ethernet port today, so it was was fresh in my mind.
I don't use the optical drive on my iMac much, but the times I have had to were not times I would have been able to avoid. I don't want yet another accessory/dongle or one less USB port. There's tons of room, just include the drive.
This came up recently with trying to install Windows inside Parallels on my girlfriend's laptop. Their IT people had a DVD and of course her laptop has no DVD drive, so I looked up how to use Remote Disc and found out that it works great except explicitly not for installing an OS and oddly almost all the other common uses of an optical disc.
These types of discs are not supported by DVD or CD sharing: These types of discs are not supported by DVD or CD sharing: DVD movies, Audio CDs, Copy protected discs such as game discs, Install discs for an operating system such as Microsoft Windows (for use with Boot Camp), or Mac OS X.
Apple also hasn't killed Ethernet, the desktops still have it.
Retrofitting a conservative GC onto C is really hard, and they were never able to fully make it work. If you look at the Boehm collector's page, you see a lot of potential issues that can and do arise. Having these issues in an optional add-on that you adopt (or not) after weighing the issues is one thing, having them in a system-component that is declared to (a) be the future and (b) "Just Work™" is another.