As V9 is right around the corner I might be a little late to the party, but after playing around with the arp for some days, the following things came in mind:
It would be helpful when the custom chord editing (long press on chord button) would also be available in the chord chain editor.
Regarding custom chords, if the notes selection is equal to any of the preset chords the display should show this chord instead.
A Tap Tempo function. I plan to use the arp in jam situations then this might become handy. Though I have no idea which button to use for this so maybe this will not happen but it would be nice.
Re chord detection, I should say that ARP only has 108 chords/scales in its memory from a possible 4000+ chords. They are the most common though. :)
Cheers for the suggestions.
1) Currently, ARP's chord chains use whatever chords are assigned to the Chord buttons, so if you assign a custom to chord 1, any chain that plays chord 1 will play the custom chord.
I am planning to add a mode to chains that allows you to assign a specific chord to the chain, regardless of the chord button assignments. This will also allow you to capture chords from an external keyboard while editing the chain. However, this is more difficult than you'd think and I couldn't get it completed for V9.
2) Solid suggestion, this is on my todo list.
3) Yes, I should have added another button in the original design. Perhaps I could make it so that if you hold the program button you could use the Play or Set button to tap tempo?