Good question.
There was a long thread here a while ago about how DOMS is no indicator of an effective strength workout. Yet over at the Collage forum I've seen people dissing a DVDs because it didn't give them DOMS, and people wishing DOMS on each other!
I lift very heavy by VF standards, yet rarely get DOMS.
I used to be obssessed with my target heart rate. I would wear a HRM for every cardio workout and constantly stop and check my heart-rate - until I realised I was just flinging myself around to raise my heart-rate and I would be better served by learning the moves and/or increasing my endurance, and once I improved in those areas, I would get a better calorie burn overall.
But if a cardio workout didn't make me break a sweat and I knew it was the workout - not me - which was at fault I would definitely sell or trade it.
As for the joy of movement thing, I have recently got into Tai Chi and Chi Gong and love them for the stress release, dynamic stretching and just because they make me feel good. I think there's a place for those types of gentle workouts in everyone's regime.