A couple of things are happening to make you sore or not sore: Your muscles are broken-down after a workout, sometimes leading you to feel DOMS (Delayed Onset of Muscle Soreness.) You may feel DOMS if: You are working out a new muscle, you are new to working out, you changed the reps to a ton higher or added alot more weight.
You may not feel DOMS if: You are doing new exercises and that muscle group is strong, you are doing a similar workout that your body has learned to adapt to, you are in shape, you took the appropriate measures with nutrition and post-workout rehab for your body or the not desirable one, you aren't working out enough!
So the answer to be or not to be sore, depends on your muscles, your workout, your time working out, how hard you workout, how fit you are and how you treat your body after the workout.
Don't get me wrong, I like to hear I made a client sore, but the good kind of soreness! The best way to measure if you workouts are working for you are: are you getting closer to your goal, are your measurements changing, and how are you feeling physically and mentally? If you are getting closer to your goal, if your measurements are changing and if you are feeling better physically and mentally, then I'ld say your workouts are working for you!
Have a great week and check out my blog for some snack updates and additional nutritional tidbits! http://reachyourfitnessgoals.blogspot.com