This is for the beta release, and most(I think all) of these bugs have been reported in the bug tracker. (Note the bug tracker is currently reporting errors... so I can not link to bugs).
I do like a lot of things about the release... these are mainly things I don't like. So please don't take this as a bad view of Ubuntu 9.10 overall... just some criticism.
Hibernation seems to not work correctly all the time(for me)... when I close the lid, and open it later it does not seem restore properly. It shows the screen, but does not respond to input on the keyboard/trackpad. Then after a bit the screen goes black. Then I need to press the power button, and then the login box comes back up - and I can log in again. This has worked for the last two ubuntu releases, so it's annoying.
Booting seems slower... and is actually slower(timed it) for me. Perhaps I need to install from scratch for it to be faster or something. Pete Shinners has some benchmarks on his blog of ubuntu booting faster for him... boot benchmarks.
pulseaudio was installed again, stuffing up my sound settings. However after removing pulseaudio, the multimedia keys on my keyboard do not work... as they used to work in the previous release without pulseaudio. Apparently the ubuntu mixer applet only works with pulseaudio now. Yuk. If you go to the sound preferences dialog, it only works if you use pulseaudio.
So pulseaudio is using 3% of your cpu when no sound is playing, or pulseaudio does not work with your screen reader... or many other reasons you do not want to use pulseaudio, and you want to remove it ubuntus gui mixer fails.
The main pulseaudio author even says the ubuntu implementation of pulseaudio is bad on his blog... so I hope this is fixed before the official release.
Changing the speed of the CPUs/cores now requires a authentication... and typing in a password... annoying!! So now I end up leaving them at full cpu... wasting power, as I need full cpu in some situations. The usability is not considered here... I think people will just use more power.
Some of my icons were messed up, along with applets I was using. eg, my firefox icon got changed into a red circled crossed with a line through it.
I leave a memory card in the memory card holder... and now ubuntu pops a message up telling me it's there each time I open the lid. Even if I press the ignore button. Annoying. The last ubuntu did not ignore my request.
Newer versions of many software packages are available... which is nice. The graphics do seem to be faster on my intel machine... again nice :) New gcc, etc etc.
Still no jack/pulseaudio compatibility stuff. Still no OSSv4 sound system packaged :( Ubuntu have made it hard to have alsa, jack and pulseaudio all used side by side. The authors of those systems have worked to make the situation better, but ubuntus implementation is not good. Better to install audio stuff yourself for this release too.
Ubuntu has old SDL, and pygame releases... unlike a lot of other platforms which have the latest stable releases.
So expect Ubuntu karmic koala 9.10 to still have bad sound, and bad support for games. I have hopes that bugs will get fixed before the beta finishes... but I don't have very strong hopes.
update: Pete Shinners has some benchmarks on his blog of ubuntu booting faster for him... boot benchmarks. Added link to pulseaudio authors blog about poor pulseaudio on ubuntu.