Older Zipps, or at least mine, were really out of balance. I suspect because they were shooting for the lowest possible weight. The bike would bounce like crazy on a repair stand when the wheel was spun. I started to look into fixing it, but in the end didn't bother to address it; it rode fine. There were times though that I could feel that imbalance pulse when riding. It didn't affect handling or induce speed wobble or other issues. It was just noticeable as a sensation.

When I was futzing around with it, it surprised me how much weight it would actually take to get it in balance -- significantly more than a chunky wheel magnet. It would have involved putting a few of the big big fishing sinkers in a spoke hole or something, and a tubular was already glued on. Everyone said, no, doesn't matter, bike wheels rotate so much slower than car wheels.

But I feel your frustration. It was a big relief when the next set of wheels, which were similarly light, were balanced. It just makes it all feel better, especially when some big hill is sending you at 50 mph.