The O<sub>2</sub> sensor thing has been going on since before the 2000 model year. My ex's L went through 2 within 10,000 miles back in early 1999.
Does anyone know offhand just what one of these sensors costs? I have not tried to look it up in the book at the parts store, but a lot of O<sub>2</sub> sensors are interchangeable, so much so that you can buy an adapter for Toyotas which allows you to use standard (spark plug-threaded) GM O<sub>2</sub> sensors. Before I decide what's "worth" it I'd like to know how much money I'm talking about.