I assume that .cbr files don't have digital restrictions built-in - with Comixology, the copyright holder can limit comic access to the buyer - same as iTunes and Kindle purchases. I assume that's why the comic companies are going with it.
Nope, it's simply a renamed .rar file for convenience. Even with drm Kindle files, I could still move the files themselves around for better organization across several platforms. Can't do that with Comixology. I understand why they and the big book publishers push it, but they are fighting a losing battle. Steve Jobs realized this several years ago and forced the music industry to conform. As a result, all music on iTunes has been DRM free since 2009. Eventually, he'll get the movie and book industry to do so as well.
That's why I like Baen Books. All their files are DRM free. Buy the book and you don't have to monkey around getting it to work across several platforms and operating systems. It just works.
As far as price point, although DC's digital and physical editions will be starting out at the same price, DC currently plans to lower the digital price a dollar or two sometime down the road. They don't want to alienate the brick-and-mortar comic shops, as that's what's currently keeping them in business. So it has to be a very gradual transition.
If they want this to work, then there is going to have to be an incentive to actually buy the digital copy. Hard copies aren't going anywhere anytime soon. The Kindle hasn't killed the printed book, nor would digital comics kill the comic book stores. Sure, there would be some closures (similar to Borders closing up shop), but the more successful shops would transition to being more than just comic shops. One of the shops in my town has recently become a catch-all geek enclave by branching out into RPGs, music, movies, etc.
-edited to add
Now, what they could do is something similar to Netflix and what Marvel does with their browser-based Unlimited subscription service. Only, make it so it can be viewed cross-platform. That way they can keep their DRM, consumers would have an in-depth library to choose from, and DC could easily get away with charging $10-15 a month for usage. Add in-app ads or whatever to keep the costs down as well.