I just downloaded the app and logged right in with my IB credentials. You would never know that Scottrade is involved.
Once you're setup it's treated like a regular IB account. In fact, when I opened my Scottrade Pro account I even had to ACAT my Scottrade IRA to IB. I have an IB login, complete with the goofy security card. And all of their TWS software is available.
It really is like having an account with IB. The difference is in commission pricing, and the fact that there's a customer support team at Scottrade that is very responsive.