The new iPad's disruptive display

The verdict is in: the new iPad has a brilliant display. Unsurprisingly, quadrupling the number of pixels on a display allows it to output crisper text and sharper images. Unfortunately, the rest of the hardware (and content creators) might be playing catch up for the next few years as Retina-caliber displays become cost effective to produce in larger sizes.
Think about the relatively recent move from standard definition to high definition (HD). HDTVs were around for years before the rest of the ecosystem (hardware and content) caught up - HD game consoles didn't arrive until 2005, the format war between HD DVD and Blu-ray wasn't finished until 2008, and bandwidth is still an obstacle for streaming HD video.

Reading

Text looks gorgeous on the Retina display, but I'm not sure if there's any practical benefit to the crispness. I still much prefer reading on a Kindle, with all its imperfections.
Indeed, text almost looks too good. Just as nostalgic artists try to emulate the imperfections of yesteryear in their digital audio and video, I believe we will see the very same thing in Retina-era typography.

The web

The first step to reading a web page on an iPad is, most likely, double-tapping to zoom in on the content column. For arguments sake, let's say that content column is 600 pixels wide, and contains an image of the same width. The new iPad is now using a 600 pixel wide image to fill upwards of 1500 pixels. It looks about as good as you'd expect (that is, not at all).
Apple's own website deals with this in the following way. It starts by loading a 1454 x 605 JPEG, which weighs 115 KB. If a new iPad is detected, it uses Javascript to fetch a 2908 x 1210 JPEG, which weighs 369 KB, and swap it with the original image. For those keeping score, that's twice the HTTP requests and four times the data consumption to make a webpage look nice on what is essentially a mobile device - with no ability for a bandwidth-starved user to disable it.
The World Wide Web Consortium are working on a solution to this, called responsive images, but who knows when their work will be complete enough for browsers to begin supporting it (and web designers to begin implementing it).
In the meantime, expect your web experience to be pixelated images set within crisp text.

Magazines

Already got a collection of iPad magazines in Newsstand? You might want to keep your old iPad around.
Most iPad magazines, including those made with Adobe's Digital Publishing Suite, are raster-based - they're basically a bunch of JPEG images - including the text.
…and if you thought the pixelated images in Safari were bad, wait until you try and read an issue of Wired with pixelated text.
So not only will all your back issues be borderline unreadable, but future issues will be much, much bigger. If a pre-Retina magazine issue weighs in at around 300 MB, expect a Retina-compatible issue to weigh about 1.5 GB.
This, my friends, is what we call going backwards.

Apps

Universal iOS apps now need to include multiple sets of graphics to cater for the various devices still in use (480 x 360 for the iPhone 3GS, 960 x 640 for the iPhone 4/4S, 1024 x 768 for the iPad 1/2, and 2048 x 1536 for the iPad 3).
This has led to significant increases in weight - with Apple's own Numbers and Pages more than doubling in size.
Perhaps not too much of an issue if you're using a 64 GB iPad, but painful for those who opted for a 16 GB iPad (or iPhone).

Games

The App Store already has plenty of games that have been updated for the new Retina display. Unfortunately I'm yet to see anything more than lipstick on pigs.
Using higher resolution textures and rendering at 2048 x 1536 doesn't fix low polygon models or clunky animation - it just makes them more apparent - and if the game was already having performance issues on previous iPads (I'm looking at you, Gameloft) they might even do worse with the increased graphical workload.

Video

I downloaded a few 1080p movie trailers from Apple, and they look absolutely stunning on the new iPad. But at roughly 75 MB per minute (based on these trailers), or 6.75 GB for a 90-minute movie, you're not going to be carrying too much content of this caliber around with you.
And let's face it, in the real world, most people are illegally downloading TV episodes and movies that are heavily compressed down to arbitrary filesizes, which look pretty bad even on the original iPad.

We'll get there eventually

It might be a decade until you're reading a gorgeous HTML5-based magazine in Newsstand while you wait for a sanely-priced, high-definition episode of your favorite TV show to download onto your 2 TB iPad 14 over your unlimited 4G connection, but we'll get there eventually.
Until then, devices like the new iPad are a glimpse of the future marred by the reality of the present.