I'm following the reason of JesseHam. I'm a professional designer (with an Adobe CC susbscription) and willing to consider Affinity for professional usage.
A replacement for the Adobe Design Standard would be quite handy to me.
However, Smart Objects are very useful: non destructive and ideal for referencing. Think of mockup design where a reference is made and can be switched instantly with a final object.
As a sidenote and please read this as a kind suggestion...
I'm quite happy with the way Affinity is going to deliver incredible software but I would like to emphasize to be crystal clear what Affinity can en can not do compared to the Adobe counterparts. If you're aiming towards professional clients that might be your early adapters, be sure not to throw them into ignorance.
As long as people know what to expect, we know how to deal with things. psd's for one are not equally the same. Smart Objects for one are not supported and opening files in Affinity Photo and exporting back again, destroys them for later usage in Adobe Photoshop (as already stated by Jesse as well)!
Disregarding features from photoshop, and not knowing this can have delicate consequences in ruining your files. Think of people who want to open and work on files from clients when they used Adobe before... Maybe Affinity can run a test while saving and/or opening, letting you know what features will be neglected (and ruined)? In this way the user is completely responsible for further decision making in the right context. This would be a huge timesaver in figuring out where things went wrong. In its current Beta state, this is completely normal, but in a final release, people won't be as forgiving I suppose.
Thanks...