I agree that having a beat sync option for the arp and sequencers would be a great feature. For those of you with absolutely flawless, robotic-level timing, this feature could still have a lot of potential for even your advanced performance flow.
For example, in arp latch mode you could enter your arp changes ahead of time so that when the downbeat hits and the arp changes to the new notes, your two hands could already be free and working other parameters elsewhere...directly on the downbeat when the arp change happens. No matter how amazing your timing is, if you have to be worried about hitting the arp change on the downbeat, it's very unlikely that you are fast enough to have your hands ready elsewhere if you want parameters to modulate on the downbeat along with the arp change.
This type of beat sync feature is very standard in the controller and dj world, which a lot of folks have become very used to. I think adding this feature would help keep this amazing synth in line with techniques that many of us have become accustomed to using. So, rather than turning this into a pissing contest of who has the most flawless timing... the real point to me is: beat sync would make parts of this synth immediately more accessible to less skilled players, and simultaneously would allow highly skilled players to go even further than they could without this feature.
It's not a deal-breaker for me by any means... but, I think it's becoming more and more a standard feature that I would always welcome.