Comparing that to my old iPhone 3G and my iPhone 5 though, you can see a significant difference. And not that I would intentionally go out and buy a retina display phone just for the retina display. Crisp but only looks prettier.
The comment BenW makes about the new Macbook Pro though is amazing. The screen on those machines are just incredible and absolutely beautiful! That and then playing around with some general internet browsing was also incredible. Unfortunately, I didn't have the opportunity to play around on one with XCode but just writing some random jibberish was nice, let alone programming and debugging.
Retina displays are quite pricey though and that's why Apple has not added it to their iPad Mini for cost reasons. They've managed to add it to the Macbook Pro's but at a significant cost. Let alone adding it to a (let's just be generous here) 21" screen would bump up the price a few hundred dollars. In saying that though, the day is coming and I'll continue to drool over that Macbook Pro screen until I can get my hands on a 21" Retina Display screen!
On the note of vertical displays. The ones at uni are 24", I think, and can be made vertical. Mate does it all the time for Reddit. The ideal setup though: one vertical screen on the left, widescreen display in the middle and another vertical screen on the right. Internet Browsing/Documentation, Application Testing/Viewing, actual program code.... *drools*