I booked a June trip on USAirways in February. The flight to MCO was a direct flight from Columbus. Well, being the paranoid OC that I am, I tend to check the ressie every now and then, and also like to price the flights that I have booked to see if the price has gone up or down.
Last week I was checking the prices, and noticed that they USAirways site didn't even give me the option of the flight from CMH (Columbus) to MCO. That's odd, I thought, but it must just be sold out -- even though other "sold out" flights appeared in the list off options, but were shaded out so that they couldn't be chosen.

So I checked the master flight schedules and lo and behold, the flight I had booked didn't exist anymore. That's VERY odd, I thought.
So I plugged in my reservation number and saw that USAir had changed my direct flight to one with a stopover in Charlotte with a two hour layover, and four seats had been preselected for me and were spread all over the plane, which isn't exactly optimal for travel with a 3 and 5 year old.

So I called USAir, and talked to a lovely CSR who went through the reservation she saw on her screen.
Her: I see you had an 11:40 flight; that's been changed to an 11:50 flight, which goes through Charlotte and arrives at Orlando at 3:44, so that's not a big change.
Me: Whoa, whoa, whoa, whoa!!! I said. Not a big change? My 11:40 flight was a direct flight that landed in Orlando at 1:45. That's a HUGE change.
Her: Oh, that can't be right, sir, you couldn't have had a direct flight -- we've never had a non-stop from CMH to MCO.
Me: Well, I'm looking at my ressie right here Flight XXX, 11:40 - 1:45, CMH to MCO. And I see on your timetable that you do show non-stop from
CMH to MCO leaving at 7:45am.
Her: Oh, yes, I see that now. But that can't be right. I've worked here for 20 years, and we've never had a nonstop between CMH and MCO. Let me put you on hold and call "inventory."
Me:
Her: O.k. Turns out that we are starting a non-stop in June, it's only on Saturdays, there's only one, and it used to be at 11:40, but is now at 7:45am.
So, with much trepidation, I asked her to book me on the 7:45am (!) nonstop rather than the 11:50 w/ layover (who else envy's my opportunity to drag a three year old out of bed @ 5:00am? But I think that's preferable making them changes planes on the way to Disney - might as well have 3/4 of a day there rather than just a couple of hours the first day!).
Long story short: (O.k. - I think that ship has sailed; maybe this is just the conlcusion to a long story) I asked her why I had not been contacted about the change, and what would have happened if I weren't obsessive-compulsive about checking and rechecking my ressie? She said that USAir has had a lot of schedule changes recently, and they are just now contacting people who might be affected by a late April, early May flight change. They would have gotten around to me eventually.
So - in sum: On balance, you are probably safe with a USAir reservation. But because of the bankruptcy, and especially with the specter of a merger, you should be diligent in checking and rechecking your flight reservations. They might change the schedule on you unexpectedly, and that might have an effect on how the rest of your day goes on those flight days. But, it seems like USAir will take care of you when things do change.