I just hope this merger is done a lot better than the UA / CO merger is going. This has been going on for 3+ years and they are still running as two airlines, even though they have one certificate. I guess it's a Union thing. Management at UA does not seem to not care about us customers.
DL / NW seemed smoother. US and HP (America West) was not a smooth transaction either. The many flts I took on US several years ago sucked. So I switched to DL and UA, some on AA.
I now choose DL first, UA second, AA third (good customer service and meals, but #3 for me - UA is dropping fast in my bookings). WN next, than US.
I used to fly quite a bit on US when they had the hub in LAS (my home base), since than no more. Please do not turn AA into a US product!