I have an iPad. I've been hankering after this sort of touchscreen media control from the sofa for many years, long before tablets and smartphones came out! I experimented with a 12" touchscreen monitor attached to a dual display PC running Meedio as it was the only media software that had any sort of dual-screen functionality, but there were issues such as dodgy dual screen control from Windows (it's really not designed for this, only one screen can run ActiveX, only one screen can have focus etc), the need to have power, VGA and USB cables attached to the monitor therefore, practically, it had to be mounted on a wall which means you have to get up off the sofa...
Windows Mobile devices were out there but these were too small for me. I wanted touchscreen control of an extensive collection of albums - I didn't want to be forever scrolling and squinting.
The concept of the 10-foot interface for use on TVs by media centers/boxes is flawed in my opinion. It's a bigger screen but simply because it's 10-feet away you can't really get any more items on it that you would on a hand-held device. And using a remote control where you have to press up and down and left and right buttons, and OK buttons and Select buttons, and Back and Return buttons, Page Up and Page Down buttons, is actually complicated, indirect and frustrating.
The iPad is the perfect size for this sort of thing. When it was announced, people said "Oh, it's just a bigger iPod". But that's the whole point! That's what makes it work and opens up a whole new area of applications that just weren't suitable for a phone-sized screen. And look what effect it's had on the market. I can't believe that PC manufacturers didn't see this coming and didn't have the foresight to do it before now, it was left to Apple to produce a smart but expensive version as they usually do and then everyone else has copied. There was already proven technology in the form of high-end multiroom home AV installations, home automation etc.
I also can't believe that J River themselves haven't forecast the rise of the hand-held remote at-the-sofa and it has been left to third party developers to take home media browsing and control out of keyboard and mouse PC environment. Even Theater View, which could be used on all-in-one touchscreen PCs if you want something wall-mounted or coffee-table, and now on Windows 8 tablets for that sofa experience, has been rather neglected in terms of touch compatibility.
Anyway, I digress! I can't see myself using anything smaller (or larger) sized than an iPad regular for this application. Your mileage may vary!