I used to use Omaha quite frequently to fly out west because it was nearly always a good $100 or more cheaper to do so. Yeah, the drive back always sucks, but it was better than paying through the nose to use DSM. In the last decade, I had found a couple round-trip fares to SFO or OAK for $140, which prompted spur of the moment weekend getaways. It's been quite a while since I've done that, though.
If you have time to plan, airlines usually drop and raise their fares periodically, and you can catch them when they're low if you're persistent about checking. I have found with Southwest that they sometimes drop fares by as much as 50% for just a few hours during a particular day before they jump back up again. I think I've only found it necessary to use something other than DSM once in the last three years or so to fly. It's certainly much more convenient.
With the passenger numbers seemingly always increasing through DSM, it would stand to reason that prices should remain at least competitive with OMA and MCI, if not be outright better every time for the foreseeable future.
