As a Graphic Design Student, I would say ONLY as a supplemental piece of equipment. It is actually really BAD at extensive Photo-editing and general Graphic Design work. Graphic by Autodesk is the best iOS app for an ATTEMPT at Graphic Design but it's WAY underpowered and it doesn't import or export AI or EPS files (PDF export is hit or miss). There is no true Page Layout software at all for iOS.
With Duet Display or Astropad, it does make a decent Cintiq alternative, just make sure you're using a MacBook Pro made in the last couple of years or it can be painfully slow.
All that being said, for illustration, it's incredible. The Pencil combined with ProCreate is one of the best digital illustration environments I've worked in over the 20 years I've been in the business. ProCreate is REALLY powerful and it's the most fluid illustration environment I've ever worked in on a tablet. It might even be better than working on a Cintiq in Photoshop or Clip Studio Paint.