Soreness might be an indicator that your body has gone into too much shock over a period of time (scientifically, it will include such things as lactic acid, etc., etc.), but as you body adapts, it will handle it better. At least, that's my experience. Whenever I start a routine after being out of it for a while, the first week or two can be a bit sore, but when I get into it, I find the soreness is almost non-existent. It's more of a fatigue localized in the muscle group I had worked the day or two before. I've even found I can push myself far, sometimes worrying I've pushed too far, yet the next few recovery days will say otherwise when the soreness doesn't come.
My best indicator(s) of a good workout?
- High energy level throughout
- Pushing weights with an unprecedented intensity
- Pushing weights to an unprecedented set of repetitions
- Pushing weights of an unprecedented mass
(i.e.
Performance is my indicator of a good workout. It actually shows I'm building muscle. I don't need to see it, so much as feel it.)