It seems that many Shopify subscribers agree that certain features should be basic to a POS and should not even require a (paid) app. Some of these have been requested for several years but haven't (yet?) been implemented.
I figured I'd list the ones I've come across. I'm certainly going to leave some out, so please add yours, and if someone wants to link the topics which discuss this, that might be very useful.
In no particular order:
1) Merging customer accounts
2) Allowing customers to send online gift cards directly to the person they wish to gift (not strictly a POS issue)
3) Open (variable) price product option
4) Ability to add staff members and pay per additional member instead of jumping to a much more expensive plan
5) Ability to turn off push notifications for in store sales but keep them for online orders
6) Compatibility of bar code scanners, not only Socket
7) Easy shipping from POS (even in the same transaction as a pickup)
Ability to edit an order after it's been placed (add/change customer, split items to different shipping addresses)