I'll start off by saying that I'm a regular JetEngine user, and I have an unlimited, lifetime licence with them. I have very little reason to purchase ACPT other than optimism for a better experience than JetEngine currently provides.

I'm rather confident in that optimism.

Not only is Mauro (the developer) a friendly, responsive, active dev... he's also got some great, unique features already deployed (and in the pipeline), and has the successes and failures of the giants (ACF and MetaBox) to study and improve upon.

I think ACPT will grow into the dev-centric, feature-rich platform many of us wish the others were, and if/when Mauro brings ACPT's roadmap to fruition, I can't see any reason not to charge as much as, if not more than his peers.

Not only do I hope ACPT eventually provides more than its competitors, I genuinely believe it will. There's some great functionality already there, some of which isn't available anywhere else.

I think this will turn into one of those deals you wish you'd bought at the time... So why not just do it?

These ARE early days, however, and there are some kickers for me.

1: No Bricks integration - BUT: The roadmap is now showing this as in progress, with an Oct/Nov release date planned.
2: Freemius licencing - BUT The roadmap now mentions that all licences will be migrated to Easy Digital Downloads - a much better system.
3: The Ui, colour scheme and entire process is a little more confusing than my experience with JetEngine. I'm not a huge fan of much of the layout at the moment, and things like associating taxonomies to post types have to be done after the fact, rather than as part of the cpt creation process.
4: Nested repeaters are missing from the roadmap. - HOWEVER Mauro has suggested that he's looking into this. This would be a feature that JetEngine doesn't have, and would make a lot of people very happy.

Overall though, I see in ACPT a lot of potential that I just don't see in any of the other players' offerings. If you're looking for something that will do the bulk of the work of JetEngine, ACF, and MetaBox, but at a fraction of the price, then this is it, folks!
If you're looking to invest in something that will one day beat the pants off those same giants... I think you might still be looking at it.

Do the smart thing; you'll kick yourself otherwise.