I am using emacs for ruby and ruby on rails. It works simply perfectly.
Exists support for exuberant ctags and autocomplete.

§£ §³§â§Õ, 09/11/2011 §Ó 21:19 +0900, Junayeed Ahnaf Nirjhor §á§Ú§ê§Ö§ä:
> Hello all,
> 
> No matter what you do, you can't achieve IDE like autocomplete on Vim. Vim offers code completion only AFTER you type in something and want to reuse. So, Vim actually doesn't work very well for me. 
> 
> Anyone tried emacs for ruby?
> 
> 
> Godspeed 
> Junayeed Ahnaf Nirjhor
> Twitter - @Nirjhor
> 
> 
> 
> > -----Original Message-----
> > From: Dwayne Henderson [mailto:its.code.in.here / gmail.com]
> > Sent: Wednesday, November 09, 2011 4:16 PM
> > To: ruby-talk ML
> > Subject: Re: best IDE
> > 
> > Check it out:
> > 
> > https://github.com/altercation/vim-colors-solarized/
> > 
> > --Dwayne
> > 
> > On Mon, Nov 7, 2011 at 6:28 AM, Uma Mahesh
> > <umamahesh_nyros / yahoo.com>wrote:
> > 
> > > Hi,
> > >
> > > Can any one suggest me best open source IDE that can be used for
> > > starter in ruby on rails.
> > >
> > >
> > > Thank You,
> > > Uma Mahesh Varma,
> > > Yahoo-email : umamahesh_nyros / yahoo.com
> > > Gmail :       nyros.umamahesh / gmail.com
> > > Skype :       umamahesh.nyros
> 
>