Right, but it still needs an email service provider to point to (and I wouldn't want to run it myself for various reasons). And the providers I've seen are expensive (for me).

Did Google stop offering a free tier for Apps For Your Domain? I guess I missed the part about being grandfathered in.

Yes. It's now $5/month/user. (plans are grandfathered however)

You also get 1TB of storage with that, and unlimited storage with 5+ accounts. I do this for my family, and we all have unlimited backups and custom domain email.

What client software do you use to access the storage and to backup to it? Is it reliable and cross-platform, by any chance? =)

I use Arq https://www.arqbackup.com

Encrypts everything, and manages the revisions. Available for Mac and Windows. I use for Mac.

Luckily, I do have a grandfathered plan where I can use Google Apps for my domain for free. But as I mentioned in another comment, I'm trying to reduce my linkages with Google, Facebook and others for privacy reasons. That's one of the reasons why I don't use that much (the other issue is dealing with changing my email addresses with everyone else I've shared those with - ad based free email providers like Yahoo do not offer mail forwarding out of their platforms for free).