Just for your information, flew Oman Air twice this month (since the change in ASR) and they were EXTREMELY clear that whatever seat you got assigned is what you'll fly into. Online Checkin didn't worked either - apparantly for everyone, since the queues were massive at the "inbound" to MCT at my local airport (ZRH) at checkin counters - since apparently everyone got told by OLCI to "show up early at the airport due to problems". 50 pax already there waiting at 3.5hrs before departure! (In my case, it was a bit of a special ticket, and thus I assumed some real issues - it was fine, though, once at the counter they said that no-one could do OLCI due to the "new system" or something like that)

So, not getting a chance to change seat is rather annoying if you prefer aisle over window (luckily some people prefer window over aisle - it was quite a "bazaar" in the aircraft!)

Also, exit row seats were left empty (only if you pay - i was two rows behind, so I overheard the conversation from people- actually just 2 pax - having paid for them), even when asking at the gate.

Result: Some just jumped off to grab the exit row seats once boarding was completed. Wasn't "defended" by the crew, who seemed very passive and not very much interested in their job on both flights.

I was decently happy in my (swapped) aisle seat, IFE is good enough in the new 787 and legroom is fine even for people above 1.8m.

All in all, flying Oman Air in Economy is doable, but they really should (and need to) work on their seat assignement system. Never seen it working so badly with so many people not getting their seat of choice at any other airline, even on fully full flights (Oman Air load was about 90% each time)