Yes, MiniKeePass works quite well on iOS, with Dropbox and owncloud sync (and I presume others, but those are the two I've used.) Oh, and MacPass for OSX.
SpiderOak does both. Their interface is, IMO, not nearly as good as Dropbox (I've never used carbonite), but it does check both boxes (backup and sharing/sync).
Bum-rushing is, IMO, strong, but the problem with striking up a conversation with someone in a line, is that they're more or less a captive audience. If, for some reason, they'd prefer not to speak with you, they have to leave their place in order to do so, and forcing that on them isn't really polite, or fair.
I wonder if some of the laughing isn't so much at you and your stack, but at the laugher's experiences with those (or similar) technologies.
We've all worked with technologies that cause us pain in our development process. Sometimes, the pain becomes so great that we look for, and find, something that we like better. Changing to this new techonology eases said pain, and allows us to be (or at least feel) more productive.
I believe it's possible that some people laugh because they remember when they used one or more of those technologies, and the pain they felt while using it. They laugh and suggest other technologies because they assume you have the same pains they've had, and they'd like to offer you what they consider a better alternative that might ease some of the pains. After all, it worked for them!
It appears that you've had some pains with this stack, but that you've found ways to deal with those pains that don't involve leaving your current technologies. Good for you. You've built successful applications on them. Also good for you. These are, of course, the things that really matter.
It still needs a bit of work, but I like hosting my own list.