Nano sound: 1G vs 2G

I've long enjoyed my first generation black nano and just purchased a second generation black nano for the increased space, increased battery life and even smaller size.

After trying it out for an hour or so, I can't help but feel that the sound quality is worse than the first generation - contrary to some of the reviews. It does seem to offer more high end sparkle, for sure, but there seems to be a substanial mid-range suckout. There are specific pieces of music that I listen to on the cardio machine very often, and I can tell that certain instruments are MIA or substantially de-emphasized.

Worse, the the overall sound seems shrill compared to the original.

Have any of you had a chance to compare 1G vs 2G nano sound?

Thanks,
Art

ps: When I migrated from the old hard drive based "mini" to the 1G nano, I felt the nano sound was far more grain-free and overall a substantial improvement. My apriori expectation was a further improvement in 2G nano.

pps: I don't use the ear buds that come with the unit. I use a sports headset from Sony for exercise and Shure 3c for quality.