AW: Few questions from a newbye

  1. Currently my main development platform is Windows, so is there any
    free yet powerful IDE for Ruby on Windows, with intelisense
    (auto-complete), debugger, etc - anything you’d expect from a good >IDE?
    If not on Windows, is there any like that on other platforms?

Well there is freeRIDE
or there is an eclipse plugin called RDT. I myself use arachno, but it
isn´t free and it´s still beta. On linux you can use kdevelop

2.bis. As I understood there are several libraries for building GUI
with Ruby, which one is the most portable one across as many >platforms
as possible, as well as allowing to develop applications with a >modern
look (I mean to have as many visual controls as possible - tables,
tabs, splitters, etc). Is there any visual designer for that?

Well there are different, i like FOX/fxruby and
there exists an gui designer (sorry, i havn´t got the link).