People are using the number of followers to @realDonaldTrump to gauge the progress. His total was 69.5K last night and is 79.5K this morning, so it may be going even faster now. Someone said they were hiring to help with the waitlist.
They are still developing features. Don’t expect full-blown Twitter features when you get on. Reminds me of the early days of Gab as everyone cheers on the development team. But everyone is so happy to be there and to not worry about being censored!
You only need a relatively small pool of users to find the biggest chunk of programming bugs. It only makes sense that you would knock off the largest number of -- but easiest to find and fix -- bugs first, then add more users. The further addition of new users will help to flush out the remaining bugs that are less common. By the time the vast majority of users are added, you've eliminated most of the problems.
It's a good approach that prevents a lot of user (and programmer) frustration.