If the AJAX error exists as a result of redesigning the Collection Tracker, then I could understand how difficult it would be going about fixing the issue. However, probably most people who use the service don't know there is a redesign, and for me personally, I didn't even notice the BETA tab until I read it on a thread. Therefore, if people can't use the current site properly, that seems to me to be a tremendous risk that shouldn't be taken lightly. I can imagine a lot of current users will be jumping ship to something that actually works, there are plenty of services out there. I'm not a web designer by any means, but fixing the current site seems to me to be a way more important priority.
I personally stuck around because I loved the site, because it's free, and because I'm excited to see what the new collection tracker will look like... Looking forward to having a stable site once again.