Thanks for the compliments! Not sure about what's causing the fps issues, but we're definitely investigating.

At the moment, there aren't any limitations after you sign in - Animatron is free, and the only difference between a registered account and a guest account is that guests can only create one project (which is only saved for 15 days). Pretty soon we'll be rolling out a few different paid-subscription plans that will offer advanced features and functionality, but there will always be the option for a free account.