TBH, they should've done this so long ago instead of sticking with making DVDs and charging $50 for them. That's where the pron industry fukced up. There's a gazillion websites to download free music and movies as well as streaming services, yet both iTunes and Netflix have been able to stay afloat and deliver. If they follow the Netflix model and come up with exclusive content, it'll help with production costs and give them a one-up on the other companies. They already own some of the most succesful studios out there right now with DP and Brazzers, so the idea has good bones.
The model can still work, though. It all depends on the quality of the service. A Roku app would be huge.