Indeed, you'd need to copy-paste four text fields
> for others, you have to contact customer support, and sometimes pay more.
That's ridiculous, I've never seen any registrar do that. Even if you do choose a terrible registrar, actual DANE rollout in browsers would put pressure on them to get their shit together.
As for DNSSEC validation: validation currently seems to happen between 0 to 95% according to https://stats.labs.apnic.net/dnssec
Obviously, for DANE to work, verification must happen. DANE-enabled browsers will enforce validation, or fall back to regular TLS (with the scary warnings if someone stripped DNSSEC for a DANE server, as the certificate doesn't work any more). On operating systems that don't bother with DNSSEC validation, browsers can still query the necessary keys.
As for performance, DNSSEC does impose extra network traffic, but so does transmitting an intermediate certificate.