A tablet beats paper any day as far as I'm concerned. Even if you're just using a sheet music page-turning app. An iPad Air is
more compact than any folder with loose sheets or book whose binding doesn't always like to stay open. That, and you can carry your entire library of music with you. If paper can do it, an app can be designed to do it better.
I'm not sure where Jim is hanging out that tablets aren't "acceptable" but it's a trend that will change fast. Five years ago students weren't allowed to have cell phones in schools. Now you're a bad parent if they don't have one. We're right in the middle of a paradigm shift.
Arguments of portability, acceptability, and convenience have zero resonance for me. I can safely proclaim that for the rest of my entire life, any time I would consider sitting down at a piano -- acoustic or not -- my tablet will be more ready than any papers. And if someone tells me I can't use it, I'll go someplace else where I can.
All of that said, tablets vs. paper is a different discussion than notation vs. piano roll... and both are moot and off-topic for the purposes of adding cool training features. All of this stuff is coming. And while there are some real trade-offs for
when they'll happen, there isn't any question of whether or not they will happen. 2013 had a lot of big IT/business/maintenance tasks get in the way: months of bug-fix-only releases, a major website infrastructure switch-over, the music store (and its associated "bring Nicholas out of 2002 and up to 2013 web technologies" phase) took lots of time away from development, two major "real life" things I never discussed shaved about four months right off the front of the year, and while Synthesia 9's multiple languages is a boon for an expanding user base, it's not especially exciting for existing users.
2014 is... completely wide open. There are only a couple small efforts (e.g., the video creator) lined up that won't directly improve the practice tool, but overall I'm really excited to have a full year to get some awesome features in. I've been saying "I'll have time for X after Y" for years now. The good news is I've run out of Y's, so there is finally time to get to some of those X's.