That’s a pretty big compromise to work in one app, switch to the viewer to see how it looks, then switch back again to keep editing.
iPad has its advocates as a productivity machine, but in my eyes it is full of compromises and very limited. Colour calibration for designers is one issue, being unable to compile code for developers is another issue, being unable to work with large files (i.e. RAW image files, EPS files) or being unable to link the images in your project to a source folder. Sure you can use a cloud solution, but going back and forth with massive files is impractical.
Surface Pro 3 (and the 4 coming in just a few weeks) wipes the floor with iPad because it can do everything the iPad can and it can do everything the iPad can’t.
I know a lot of people disagree with me, but IMO Apple should have put OS X on the iPad Pro because they can call it a productivity device all they want, but it’s only that to a select group of users.