I love circuit workouts and AWT but I always do them every other day, usually Mon/Wed/Fri.
Like LuckyStar said I worry about aggravating my joints.
I try to go for a cross-training effect by alternating circuits/awt days with either:
a) HIIT cardio on my elliptical (CardioCoach)
b) power yoga / pilates / or some other stretching type workout (KV's YogaSculpt; Kari's ALC II; Bar Method etc...)
c) Kickboxing (if I feel up to it)
d) swimming or walking
hth