Ubuntu 9.10 Karmic Alpha 4 is now ready to download and test. This is a great opportunity to boot your machine with a LiveCD (or USB image) and check out to see if there any regressions - and if so, please file a bug so it can be fixed before the final version is rolled out.
I'm currently running Karmic on my laptop and servers. I'm really impressed with the improved boot speed and the Kernel Mode Setting (KMS). KMS is especially effective with suspend/resume and also reduces the screen mode transitions during boot.
So download a suitable Alpha 4 image give it a try!