So far there have been six alpha releases of the forthcoming Ubuntu 9.04, due for final release next month, and late yesterday the one and only beta release was made available for download. From this point forward there's a release candidate in mid-April, before the final release is made on the 23rd.
With this beta release everything should be shaping up nicely, and (theoretically) the work from this point onwards should be bug-fixing and polish.
Let's find out how the release is shaping up.
One of the things demanded by Ubuntu head honcho Mark Shuttleworth in his announcement of 9.04 was that boot times should be improved. This certainly seems to have happened, and in my tests 9.04 booted pretty quickly. In fact, booting to the login prompt was actually quicker than resuming the machine from hibernation. (My test machine was a crappy budget laptop with a Celeron chip and 1.5GB of memory; I did a full hard disk install.)
Additionally, the ext4 filesystem driver is now included, although isn't used by default, and must be deliberately selected by the user during partitioning. The big boasts of ext4 as far as end-users are concerned include support for insanely large file systems of up to one exabyte, but the feature that's got most people excited is a performance boost compared to the older ext3. I ran some quick and unscientific tests on an ext3 installation of Ubuntu, and then repeated the tests of an ext4 install. The testbed was the aforementioned budget laptop, and the highly-accurate timing device was myself, my thumb, and the stopwatch mode of my wristwatch. In other words, don't hold too much store by these results.
There were some marginal improvements with ext4, especially in boot times and when copying significant amounts of files, but perhaps not enough to overcome the potential risks of using ext4 this early in its life. (You might be wondering if the hibernate to disk performance is improved but remember that Ubuntu hibernates to the swap partition, not the filesystem, so this is unaffected; I realized this after performing my tests, but it was borne out in my results which were virtually identical between filesystems).
Boot from cold: 25.93 seconds
Start Firefox on a cold machine: 4.64 seconds
Start OO.org Writer on a cold machine: 7.11 seconds
Copy /usr directory to the desktop (1.5GB; using cp command): 6 minutes, 6.62 seconds
Hibernate to disk: 29.21 seconds
Hibernate wake-up from cold: 30.86
Boot from cold: 22.23 seconds
Start Firefox on a cold machine: 4.35 seconds
Start OO.org Writer on a cold machine: 7.74 seconds
Copy /usr directory to the desktop (1.5GB; using cp command): 5 minutes, 21.48 seconds
Hibernate to disk: 29.56 seconds
Hibernate wake-up from cold: 29.91 seconds