I'm a big fan of Mozilla as well, but can Firefox Sync handle credentials other than for web? I use KeePass2 to store a lot more than just web username/passwords. Also, I like to keep my password database separate from my browser for security reasons.

As far as trusting this project, it is GPL and you are free to inspect it. I don't think being part of the Mozilla Foundation somehow guarantees secure code. If the author wants $60,000, he is free to ask for it.