I had been a moderate supporter of UA, but as others said the merger has created big issues for Customers. Reservations are disappearing, upgrades are getting passed over, I've experienced unreasonable delays with horribly inaccurate updates/information and employees are not happy. I would not move from a stable airline to this plane wreck right now. There is a chance they can clean things up, but you don't want to deal with the nightmare if you don't have too.
UA is an absolute mess right now - stay clear.