I'm happy to see an apology, but there are further steps they could take. I just did a clean install of Firefox and unless I somehow messed that up, it looks like user studies are enabled by default. Someone correct me if I'm wrong here, as I didn't expect that to be the case.

They should absolutely not be running any sort of user studies on people who may not be aware it is being done, which is going to be the case with the current setup. The only way it sits right in my mind is if user studies are opt-in instead of opt out.

This is especially ridiculous as their marketing is focused on respecting privacy. An apology is nice, but changing this setting would go a long way towards proving that.