I've learned to love and hate Back to My Mac since I purchased my iMac last fall. In theory, it's great to have a lifeline to my files that's faster than a Backblaze restore and broader than Dropbox. And beyond that, there's the promise of using Screen Sharing to make my desktop computer somewhat mobile, as long as I have a device with a large enough screen and fast enough internet connection. In practice, since my home upload pipe is pretty wide, both file and screen sharing have been flawless…as long as I can connect.
All Back to My Mac really does is keep track of the public IP addresses associated with your Macs and make that information invisibly available via iCloud; the connections then happen over the AFP and VNC protocols. But even if that address doesn't change, should Back to My Mac somehow lose its record, your Mac is adrift in the vast sea of the internet, inaccessible. Sometimes that's an inconvenience; sometimes it's a disaster, if you're counting on remote access — something I've trained myself out of doing.
There are 1,001 things that can go wrong across the local and wide area networks that separate two Macs. On a couple recent occasions, I've solved Back to My Mac connection failures by restarting the client computer, not the host. Other times I've simply been at a loss to solve anything at the remote end. I've thought about setting up some kind of recurring script on my iMac to refresh Back to My Mac, but I'm not sure whether it would help or harm reliability.
I do wonder if my reliance on a cheap TP-LINK router causes all of my problems. It delivers perfectly fine coverage and speed in my home, but its NAT features are a mystery to me and, it seems, to OS X. I know that there is one Back to My Mac feature that does require an Apple router: waking a sleeping Mac by sending a "magic packet". Whatever I saved on my router purchase, I've probably already paid back in electricity bill (and broader environmental impact) by forcing my iMac to never fall asleep while I'm out of the house, just in case I want to access it. It's a price I'd be willing to pay if leaving my Mac on always would guarantee always-on access. I know Apple can't account for every peculiar home network configuration, but I wish the path back to my Mac was a little clearer.