I have made the complete switch. My home development machine is no longer Windows XP, no longer dual booting Ubuntu but a full-fledged Ubuntu. After installing the dual-boot, and my machine at work this is the third time to install an ubuntu machine, and getting everything ready for ruby development.
I just want to archive my steps here, so a next time could be even faster :)

Installing Ubuntu 10.04 itself is a piece of cake.

My first step after the installation is to enable numlock on login screen (i always use numbers in my passwords)

sudo apt-get install numlockx

Then run sudo gedit /etc/gdm/Init/Default and find the line

exit 0

and add the following code above that line

if [ -x /usr/bin/numlockx ]; then
  /usr/bin/numlockx on

Secondly I install rvm for multiple rubies. We first need to install any ruby for that. Take the default ubuntu version (1.8).

sudo apt-get install ruby rubygems

This does not install the latest version, but we don’t need that yet. Rvm will solve this for us.

Install rvm itself:

sudo apt-get install curl bison build-essential zlib1g-dev libssl-dev libreadline5-dev libxml2-dev git-core
bash < <( curl http://rvm.beginrescueend.com/releases/rvm-install-head )

Then make sure rvm will work always

sudo gedit .bashrc

and replace [-z $SP1] && return with

if [[ ! -z $SP1]]; then
  .. original content that was below the && return line
  [[ -s $HOME/.rvm/scripts/rvm ]] && source $HOME/.rvm/scripts/rvm

Then rvm should be available.

Install the needed rubies. We use ree at work, i like to work with 1.9.1/2 and i want to check out rubinius. So install your rubies through rvm

rvm install ree
rvm install 1.9.2
rvm install rbx

Installing ruby 1.9.1 was a bit harder, when i just tried to run the standard rvm install 1.9.1, i received the following error:

.rvm/src/ruby-1.9.1-p429/lib/optparse.rb:1310: [BUG] Segmentation fault

and that was caused because i use a newer gcc version, which can’t handle the -O3 optimisation. It took me a while to find how you can fix it, but in the end (as always) it was easy.

Just type

export optflags="-O0"; rvm install 1.9.1

To end, set your default ruby version

rvm ree --default

now all your new sessions you should be using your selected default version.

After installing your favourite editor (Netbeans or rubymine), your favourite database (postgreSQL, sqlite, mysql ), and your list of gems you are ready to roll some ruby!

I must say as an previously avid Windows user for ages, i am very impressed by Ubuntu. This is a free operating system, and while i was aware that everything just works better being linux (meaning processes and filesystem); but not only that: it even looks better and is very user-friendly. It is way more customisable looks-wise then silly windows. In Windows 7 for instance you have to use this very large font, and in Ubuntu i can set the size to anything i want (small!!!). Awesome :) And i guess it will amaze me for the next few days and weeks whilst finding out other new stuff.

[UPDATE] For me it is confusing that the minimize, maximize and close buttons are on the left-side, i think it is done to be more apple-like. But the fix to move the buttons to the right is luckily very easy once you know it :)