CodeIgniter vs other MVCs and User Authentication

[eluser]Unknown[/eluser]
Hi,
I am new to MVCs but I do program with HTML,PHP, and MySQL. To start, what are the main advantages with using CodeIgniter over some of the other MVC frameworks?

To start learning I want to create a simple register/login website. Are there any good plugins people here have used for this so that I don't have to program everything?

Also, most of the tutorials aren't for the new version 2.0.3. Does this matter if I want to learn from them?