I've also been experiencing this issue with my sonic. I've had it taken in and they reset the TCM and ECM to see if that would solve the problem. It shifted within a reasonably good RPM range for the first day and a half with no jerks between shifts, then back to higher RPMs and jerky shifting. I took it back a second time for them to figure something else out. And keep in mind I had dropped my car off at the service shop at 7:30am... I didn't get my vehicle back till around 6pm. And all they had to tell me was that they called GM and compared it to another newer vehicle (the Volt or Cruise). And they were told that the Sonic, along side either the Volt or Cruise (I can't remember which one they said), both have six-speed transmissions (which "just came out this year") and that the computer system on those cars are trying to compensate for "your" driving habbits (how much fuel is being injected, how fast you're already going, etc...) and that it is trying to get you the "best fuel ecomony" with your driving, SO... it will naturally hessitate to shift a "little".
I don't know how true that is, since I've never driven any of those other vehicles. But with my experience with having other vehicles, I've never had one that had to run up to, or exceed 3,000 RPMS to shift over. Not in my 2007 Ford Focus, or my 1996 Ford Explorer. And not to dis on Chevy or Ford, but my piece of crap Explorer runs better than my 2012 Sonic... What's wrong with that picture???