The smart move now will be to wait 2-3 months before buying the Retina Display machine. I'm convinced that by the launch of Mountain Lion the OS will let you use the full resolution of the machine for UI, also it will give some time to other apps to upgrade their UI in order to support the new resolution.
While the upgrade to Mountain Lion will be free, I have a funny feeling that Adobe will charge (or at least will try) you some extra money for an updated version of Photoshop for Retina Display MacBook Pro :).
Any self respecting company or individual developer will probably provide a free upgrade for the UI of their applications soon in order to support the new resolution.
Why? Apple products have always been such that to gain maximum "value" they need to be bought at launch. And isnt an OS upgrade going to be 'just' $30?
The keynote and Apple website point out that all purchases of Macs from now on will come with a free upgrade to Mountain Lion once it's released.
I wonder if the free upgrade will be the App Store version that allows you to install it on all authorized versions. If so, this could be an advantage to buying after the Mountain Lion release, since Macs that come with newer OSes generally don't allow you to upgrade your other Macs to the new OS.
The way it works now when you get a new Mac, the iLife apps (and presumably Lion) are "granted" to the Apple ID you use to register the computer. Thus you can use that ID to install them on other computers.
Instead of giving you the real pixels with a DPI setting, they hide them and create the retina/non-retina modes for applications, so you have to pay for "retina-enabled" apps. A whole new way of sucking money out of apple users.
You won't pay anything more. Pro Apple apps just got a free update to Retina-enabled, regular apps will get updated with Mountain Lion, and third party apps will also be updated for free.
I don't think you understand what this high-DPI thing is meant to be and how it is supposed to work. Giving you the real pixels is not an option, because every asset of every app would have to be updated or look tiny and be unusable.
It doesn't even make sense what you propose, because retina screens are meant to give extra detail for same sized elements, not merely extra pixels -- nobody needs 5MP in a 15", whereas the extra detail is easily appreciated.
There's no guarantee that 3rd party developers will provide a free update. They could release Foo HD alongside their Foo app and make you buy it again.
While the upgrade to Mountain Lion will be free, I have a funny feeling that Adobe will charge (or at least will try) you some extra money for an updated version of Photoshop for Retina Display MacBook Pro :).
Any self respecting company or individual developer will probably provide a free upgrade for the UI of their applications soon in order to support the new resolution.