Graduate Student looking for e-reader advice

Hey all, trying to figure out what is my best option. I am tired of being on the plane or subway for long trips and not being able to do work from my 10" HP netbook (Too often it is not advantageous or possible to keep them open with people moving,seats back impeding work space etc). I've been told to get an IPad or IPad 2, but the Kindle models look nice also.

Here's what I'm looking for:

-Able to read/comment on PDFs with ease
-Option to buy E-books of current texts to save money
-Able to type in comments, notes, ideas for articles and further research, etc
-Online browser capabilities during airport layovers

Are there any good comparison threads out there of the different types of readers/tablet pcs? Thanks for your advice!