Well, well... after spending a night optimizing some graphics code I noticed I could upgrade to the new version of ubuntu... Jaunty 9.04 on my laptop.
After an hour and a half, of installing (which I had to come back to about 8 times because it had stopped to ask me questions mid way)... I came back to a new system.
Ya! I thought. Apparently a faster boot, and other such goodness... and all fresh packages as well!!!
However my boot time is now slower. It also takes longer for everything to start after login.
Also my graphics are half the speed they were before upgrade. This is non-3d stuff too... 3d 'accelerated' stuff takes a much larger hit.
Moral of the story? Don't believe the hype... and also wait until others have upgraded first before you do to try it out.
I think the graphics slow down is related to this bug ... reported in november last year.
So if you have intel graphics... DO NOT UPGRADE YET!!! If you do, everything will go really slow. If you have a laptop, chances are you have an intel graphics chip. Not really sure how the ubuntu people let such a massive performance regression affecting most laptop users get through.
Now... that graphics code I was working on before the upgrade... even slower now! hahaha. At least it sets me a new coding challenge. Fun ;)
I changed this in my /etc/X/xorg.conf
Identifier "Configured Video Device"
Option "AccelMethod" "UXA"
I added the Driver, and Option lines... and now graphics are almost as fast as it was before in Ubuntu intrepid.
Also just tried my laptop with a second monitor attached... and it actually works ok now. Brilliant.
Update 2: after I made that xorg conf change, video playback is much smoother than even intrepid now... if only they autodetected the computers properly to add those 2 lines for everyone else with an intel chipset... not everyone knows how to edit xorg conf files.
Update 3: after an automatic update today, the xserver and compiz were upgraded. Afterwards video was slow again... using 90%/90%+ core1/core2.
After disabling compiz video was smooth again, and the cpu usage went down to 40%/60% core1/core2.
To disable compiz: 'right click on the desktop, select "Change Desktop Background", click "Visual Effects", click the "none" option'
Here's hoping the next update doesn't slow it down again.
pps. the link to open the bug in your web browser from the update manager seems broken. Luckily you can copy the bug link to clipboard and manually open the bug.
Update 4: a few people in the comments left some more tips and their experiences(generally happy with improvements). One related link is: https://wiki.ubuntu.com/ReinhardTartler/X/RevertingIntelDriverTo2.4. From that page a link to https://wiki.ubuntu.com/X/Troubleshooting/IntelPerformance which might be some use to people.
Another thing I noticed... my track pad is now much better. Before it used to trigger a mouse click sometimes when I was typing - and now it doesn't! Also the little up/down scroller works again(but not the left/right one).
One issue with my monitor plugged in(which now works at full res in this release) is that if I close the lid of my laptop, turn the monitor off, and then my laptop goes to sleep. However when I open the lid to my laptop the laptop screen doesn't come on. However, a work around is to make sure the external screen is on - and then the login appears on the external screen... and once logged on, the laptop screen can be turned on with the Fn-key + F8(CRT/LCD).
I had another xserver/video driver update, and this time things didn't slow down.