Soreness may not be the only indicator of a good workout, but it's not a bad one either.
Lactic acid accumulation is no longer considered a cause of DOMS. It's now generally accepted to be the result of damage to the muscle ultra structure and connective tissue.
The resulting cellular inflamation and concomidant imperceptible swelling triggers nerve endings that cause pain. That's why the pain is delayed and why it lasts a few days. The inflamation takes about a day to kick in fully and then a few days to do it's job and abate.
Thus soreness/DOMS is a direct indicator of muscle damage that we know is necessary for hypertrophy.
Oh yeah, BTW, whatever you do, don't ice it!