Personally, I LOVE the changes made in the 2nd Gen Nano. Not crazy about the candy colors - I wish that they had gone with colors that were a little more sophisticated and subtle - And I wish that the 8GB had come in at least Silver as well as black.
Still, I got the black 8GB Nano to replace my 1st Gen 4GB Nano - And I couldn't be much happier. The feel of that midnight aluminum is much more pleasing than the chrome and plastic of the 1st Gen...the rounded edges make it feel much better in the hand.
Even though it is thinner and lighter than the 1st Gen, it still feels more solid and less fragile. With my first Nano, I felt like I HAD to use a case in order to protect it. I ended up using a CoreCase in a silver aluminum (
http://www.corecases.com/home.php). It was the least bulky hard case I could find that fit in with the Apple style. But it still added bulk to the Nano.
With my new Nano, I do not feel the need to cover it up as much, thus keeping the "WOW" factor of something so small being able to deliver that much power. Plus, the aluminum is less prone to scratches and fingerprints - a very nice feature!
I also prefer the click wheel with the middle Select button that is slightly concave instead of rounded - It just feels better and more natural.
I know others have viewed this change as a step backwards - back to the days of the iPod Mini. But I've always felt that the Mini was one of the best iPod designs out there - and this new Nano is even better! NOW, if only they could come up with BETTER colors, these Nanos would be nigh on perfect!