CEL light came on in my wife's Regal. We took it in yesterday. Apparently there's a service bulletin from GM about a PCM problem. They reflashed it. If it pops up again, they'll have to replace the PCM.
I'm NOT happy.
I looked at the Buick forum and there are several threads with people complaining about engine/transmission problems.
What preceded the CEL was an acceleration problem. When she stepped on the gas, it would hesitate, then jerk forward.
Since you have a different engine, this probably doesn't apply to you though.