GUI toolkit extravaganza!

Lately I have been looking for the right toolkit to do some GUI coding. As it turns out, there are quite a lot of GUI toolkits available that are coded in Ruby or have Ruby binding's. At first glance, they rather seem not so different from each other. So it's time to put the candidates on the line and take a look at each one's pro's and cons. I am a bit biased in this comparison offcourse, since I do have my own specific needs for a GUI toolkit. So don't expect a fully scientific comparison here, this is biased, quick and dirty but I'll do you a favour and leave the religious aspects aside.
Personally I am mostly interested in a cross-platform toolkit that provides the most functionality but above all is fast and simple. Basically, I'm too lazy to learn multiple GUI toolkits, so I want something simple and cross-platform. Off course it should look good on various platforms too!

The usual suspects I have round up for you are:
Ruby-Gnome2
FXRuby
WXRuby
Ruby Cocoa
Shoes
Monkeybars
QtRuby

We shall compare these toolkits in the following blogposts on the following aspects:

ease of installation
What do you need to do to make it work. Install a Ruby Gem or compile from source? Are there any packages for different Operating Systems that ease installation? We will look at the ease of installation in general, and provide examples for Ubuntu Linux in specific.

documentation
Is there any online documentation, how about how-to's and faq's, are there any books on the subject, how about discussion groups?

supported platforms
On which platform can you program this toolkit? On what platforms does the toolkit run?

complexity
We will use a simple window with a title, a button and some text to see the difference in complexity. Remember, this is just quick and dirty.

functionality
What can you do with the toolkit? This will be a hard one to answer since this is just a quick peek at the various available kits. The documentation will be used as a primary source to assess the provided functionality.

performance
Did I write this was not a comparison with solid scientific fundaments? Well, I will just take a guess at the performance of the toolkit. Since I won't do some measurements it's just a subjective guess.

looks
This one is also subjective to one's personal taste. I'll post at least one picture so you can judge for yourself, but along with that you'll get my opinion for free :-)

We'll take a look at the first GUI toolkit, Ruby-Gnome2, in the next blogpost so stay tuned!