I\'m new to Ruby on Rails and so far, I\'m having a lot of fun learning it. Coming from the .NET world, it\'s been quite a switch as my IDE (Visual Studio 2008) sort of hand
Whenever I attempt to learn/adopt a language/framework, I try to do things with a barebones editor... Syntax highlighting... then as I learn, I like to add things like on the fly syntax checker (netbeans is awesome at that). Then as I progress and learn the magic of the language/framework I begin to add things like snippets/code completion. At some point you might see a tool that better suits you but doesn't have something like on the fly syntax checking... but at that stage it will no longer matter due to your progression.
Personally, I use netbeans with the jVi plugin... syntax highlighting, syntax checking, debugging and everything come pretty much out of the box... (the jVi plugin required a little customization though).
However, I do occasionally use textmate or vim with rails.vim
I too was using RubyMine; it's an excellent IDE (naturally, being a JetBrains tool), but as a fairly new Rails guy, I found it doing just a bit too much for me. It tends to obscure what's really going on behind the scenes. However, for someone who has gotten accustomed to being able to step through code in a debugger and inspect variables, RubyMine was incredibly helpful and actually added to my understanding of the code (and of course Netbeans and others can do this too; I just really like how RubyMine "handles").
So in general, I say what most other people say: there are facets of IDE use that make things much clearer; just make sure the IDE isn't becoming a crutch.
If you are coming from .net/VS background, i say go with an IDE. i am a c# developer who work with ruby and rails on my free time(so i am not a 'professional ruby guy) and as Jack Ryan above said, we .net devs are used to a certain way of learning things. it is easier to learn stuff when you have an IDE showing you auto complete options and the relating documentation side by side. this way you would learn fast.
But for something like running generators, rake tasks, tests...etc you can use the console in the beginning (hey you can use a console and a IDE together right? :)). that would give you an idea of whats going on 'under the hood'. later on you could use your IDE's 'runners' or whatever to run the same stuff with a GUI.