I completed CLX a few months ago and have all of Cathe's strength workouts including STS, though right now my experience with STS is limited to the leg workouts in Fitnessfreak's Get Ready for Summer 2010 rotation.
I like Chalene much more for cardio - I reach for her workouts when I want a less structured, fun/good music workout that is step-free and easy to modify for low impact. I have even been swapping in some of her workouts for the step workouts in the rotation I am doing now because at 43, my feet/ankles/knees just can't deal with 3 days of step per week.
The weight work in CLX was okay but not as effective as Cathe's in my experience. I didn't get as much deep fiber recruitment like I get with, for example, the holy-cow paper plate exercises in STS. Some of the compound exercises in CLX were okay, and the overall structure was logical but just not as focused as Cathe.
I agree that CLX got boring and by the end I was really craving some warm-up and cool-down variety; her personality style also got irritating and I craved a "cues only" setting like P90X provides. I was also not a fan of the cardio/circuit workouts; Cathe's Drill Max and Shock Cardios are better structured IMO. I could see myself doing limited 1-month rotations using CLX and Turbo Fire in the future, but probably never more than a month at a time.