Yes, we are quite worried. Worried enough to forfeit $350 in airfare on United and spend $800 with Delta.
We have almost $800 in United travel vouchers and have been watching their website for good connections for Christmas. I drove 1.5 hours today (one-way) to buy the tickets and they told me to expect major schedule changes. DH and I got cold feet. I don't want to spend any more money with them and has a horrible schedule, too.
We are flying with an infant this time and the connections were not so great as is. With Delta, we have non-stops and reliability (!)
We have never flown on United that they did not do a major schedule change, involving hours in layovers.