> it's also completely opt-in - no tricks where you can't find the "x".
Opt-in means the X is not checked by default.
Opt-out would be where the X is checked, and people have to find/un-check it.
Opt-out is disallowed (ethically and/or legally) in many situations.
I don't know if you're truly doing opt-in or -out, but I wanted to point out the difference.
Opt-in is how you avoid unpleasant surprises. When it comes to email marketing, some even advocate double confirmation: You opt-in, and get an email where you have to click a link to confirm you really do want it.