Yes they are worth it.
I think though that you need to do a little reading on the topic. The implementation is not hard, usually 5-10mins of 1-2 exercises (essentially a warmup) that target stuff you have just trained or will be training (dependant on goals/focus). What is hard is getting the right balance or exercises and intensity for what you are trying to achieve.
Also you have to have the spare time. I've done feeder workouts for back, chest and legs before. Mine basically was some sets of chinups, pushups or squats done either in the morning after or before a workout. Morning after was about recovery, getting the blood into the muscle, morning before was about stimulating the muscles prior.