The change was made Thanksgiving week, or shortly thereafter, in 2010. It was definitely in place by January 2011.
I rode WAS/CHI second week of Dec 2010-they already had the enhanced then. Was impressed. Also had a high performance SCA on that trip.
Just rode WAS/CHI on Feb 2-excellent service in diner, crabcakes quite good. SCA was less than adequate, but another passenger did tell me he (the SCA) was sick. However, he (the SCA) wasn't so ill that he couldn't laugh at the videos he was watching.
Rode again, CHI-WAS on Feb 12/13. SCA was adequate, but nothing special.
Not such great service in dining car. Had the same server for two meals. Dinner was passable, but only passable. Breakfast service was less than adequate. That was the fault of the server, not of the chef. And there were only 4 diners, including me and my partner, when the server seemed to think that texting and/or playing angry birds was more important than serving.
In my February round-the-country trip, I was surprised that the CL was noticeably poorer service than on my other segments [which included SWC, Surfliners, CS, Cascades, EB]. Had fantastic service [from every position in dining car] on eastbound EB-really hated to say goodbye to them. And every one of them had fewer than 5 years with Amtrak, so were fairly new to the positions. For all my long trip, the personnel at the meal seemed to make more impression on me than did the plastic-or-china presentation.