I installed Ubuntu 9.10 from scratch on our Lenovo Ideapad S10 (which was running 8.10 earlier) some days ago, and I also had the opportunity to install it on a friend's new S10-2. There's very little to report in either case. The installation itself was perfectly ordinary.
When I booted up the first time, the Broadcom BCM4312 wireless interface
didn't work. I knew it used wl.o under 8.10, but that file
was nowhere to be found. A bit of research (which I really should have
done before I reinstalled) showed that I needed to install the
dkms and bcmwl-kernel-source packages, and the
wireless interface worked fine thereafter. I was lucky to have no other
hardware problems.
That apart, my first impressions are all positive. 9.10 really does boot up faster (35s vs. 55s for 8.10). The interface is also noticeably more responsive, but too many things have changed for me to try to isolate a cause. Everything seems to work nicely, without any need for tweaking. Suspend and resume continue to work correctly.
Upgrading also fixed the few niggling hardware-related problems we had. Tapping and scrolling with the touchpad works much better, and the audio problems are gone, including the excessive feedback (which I thought was due to a faulty microphone). Recording through the internal microphone works fine, and the built-in speakers are no longer inaudible. I don't know yet what effect (if any) the upgrade has had on battery life.
I'm very happy so far.