Of course you need another toy!
Plus, if you want to read outside, an e-ink screen is far superior.
I have an iPad, an iPhone 4 and a Kindle 3 - for pure text (fiction) I prefer the Kindle, and for non-fiction, I generally prefer the iPad because of the large screen. For reading, the iPhone is a backup and good for travelling light. I can certainly see the difference of the iPhone and iPad and the retina screen is definitely superior - but the larger screen outweighs the difference for me. Now, if the choice was between a retina screen and the previous one...