Signup was painless, easy and typical. Really just pick a password and confirm your email address and go. I started about a week late so I'll have to catch up, but it was nice that they allowed this and didn't close registration.
The first lecture walked through all the features of their platform (branded "Complexity Explorer"). I thought it'd be a waste of time but the walk-through was very helpful. The platform is very nice and full-featured for something they've done themselves. It compares favorably to the big dogs like Coursera and Udacity.
I'll have to dig into it a little and see if it is truly something they've done on their own or if it's something white labeled off-the-shelf.