It's something I want badly, and a portable workstation is something I've avoided buying for a while now because nothing has really gotten everything right in comparison to the iPad. The iPad's principle strength IMO is the hardware design. The iPad form factor is ideal from size, aspect ratio, weight to build quality, and extends to the internals which by their nature require no fan and run silent with long battery life. It's able to take quite a bit of travel abuse and is a comfortable size.
This is mostly why I've been hoping for an Apple stylus solution. I love the Surface in theory, and have used all the models extensively, even having bought and returned one. Yet the device has never really felt ready for prime time, and each model has been plagued with issues from software to hardware. I will say in terms of form factor the new Surface 3 is almost there, and hopefully a Surface 4 with some more powerful internals and Windows 10 would finally get it right. I also am optimistic that MS bought n-trig, so stylus support can be improved (no squigly lines, better accuracy, etc.)
The problem is even with all that, it's still not better than a Cintiq. I have a 13HD and the quality and feel of the pen is unmatched by anything else I've used. The Cintiq Companions are nice, but suffer from many of the hardware problems the Surface does. Too big and heavy, loud fans and runs hot, poor battery life. Although mercifully, no overengineered kickstand.
So yeah, I feel Apple is well primed because the hardware is unmatched. If I'm being honest I even love the lightweight OS. The art software available for iPad is already very good, and all I really want for portable use, where the complexity of full PS just isn't needed IMO. Unfortunately the capacitive screen just really limits the performance of 3rd party styluses. It's workable but FAR from ideal, and official stylus support that actually works well would be an outstanding addition to the product - and not just for art. It seems tragic there are so many nice notetaking apps out there which are actually quite popular but perform like total ass, if we're being honest. Not even close to replacing a notepad.
Of course my dream device has always been a true digital sketchpad that eschews the bloat of everything else in this category. Just something like iPad form factor, with nothing but a suite of apps or single drawing program that is the core of the whole device. Maybe a web browser too
. I'm still sad we'll never get to see the MS Courier, because that product came closest.