If you install Ubuntu 10.04 and you're running Drupal sites, you may want to downgrade the installed PHP 5.3 to 5.2, as though recent Drupal core is mostly 5.3 compatible, some contributed modules aren't yet.

Owen Barton pointed me to this handy set of PHP downgrade instructions that had worked for him.  These instructions purge the current PHP5 apps, "pin" the apps to the karmic (9.10) repository, add the karmic repositories to your source list, and then reinstall the primary apps (php5-cli, php5-cgi and libapache2-mod-php5).

This all worked for me, too, but I have a couple additional suggestions:

First, before you start, run:

php_installed=`dpkg -l | grep  php| awk  '{print $2}' |tr "\n" " "`

This saves a list of the additional PHP apps and libraries that you'll want to re-install when you're done.  You can view them easily, of course, with:

echo $php_installed

Then run KAndy's script.  Once complete, to get the rest of your installed PHP packages, run:

sudo apt-get install $php_installed

This worked for a lot of my packages, but one of my packages was phpmyadmin which required php5-mcrypt, both of which are in the "universe" repository rather than the "main restricted" one.  So I added these four lines to my /etc/apt/sources.list.d/karmic.list file:

deb http://archive.ubuntu.com/ubuntu/ karmic universe
deb http://archive.ubuntu.com/ubuntu/ karmic-updates universe
deb http://archive.ubuntu.com/ubuntu/ karmic multiverse
deb http://archive.ubuntu.com/ubuntu/ karmic-updates multiverse

After running "apt-get update" again, I was able to add all of the rest of my packages.  Instead of adding these manually, you could also replace line #10 in KAndy's script with:

egrep '(main restricted|universe|multiverse)' /etc/apt/sources.list|grep -v "#"| \
sed s/lucid/karmic/g | sudo tee /etc/apt/sources.list.d/karmic.list > /dev/null

I'm really enjoying Ubuntu 10.04.  And so is my wife as it has fixed several stability issues on her Dell laptop.  I think you will, too!