Today (the day the promo went live) the promo is on the main Choice Hotels page, whereas it wasn't there the day before. So today I was able to verify that I was registered "already" (and print it out this time) without having to explicitly go to /earnafreenight.
(Maybe I'll get a confirmation email that I registered someday, but as I recall, even when those come, they don't tend to come in a very timely fashion.)
But I'm sure all of the problems I mentioned above are intermittent. Certainly the one with Firefox periodically saying the login was unsuccessful (over and over again) has been popping up periodically ever since the new site appeared, but far from a majority of the time, just randomly.