I'm not surprised that Apple are quitting on this application. They were really developing it early, and slowed their enhancements quickly, sitting on their laurels.
I saw the app when the released it, and it wouldn't run on my then current machine. The system requirements pushed desktop machines, and my older desktop machine wasn't a match for my laptop computer. Aperture made great use of graphics through OpenGL and few of their machines were capable of giving it enough.
Apple has a terrible habit of producing good hardware or good software but rarely produces good matches on the desktop. It's as though they don't communicate with themselves. If you look back at the early PowerPC machines, they were very powerful, yet Mac OS 7.6.x (or Mac OS 8.x or Mac OS 9.x) didn't take advantage of them properly. When I installed BeOS on my PowerPC 604e machine, I was shocked at the display of power--power Apple were wasting.
In photography in 2004, there weren't good raw development applications. Thankfully, Olympus' JPEG engine created really good JPEG files, and the E-1 also created TIFF files, which were definitely useful in business.
Time passed, and I was part of a discussion that led to the Silkypix raw development application. I downloaded it and tried it. I found it to be odd. It wasn't Japanese odd--I'm Japanese. It was like so many programmers' projects--great on the inside, lousy on the outside.
I tried Adobe Camera Raw through Photoshop. I really don't believe that Adobe ever understand that their applications should work with you, not against you. They just don't seem to want to fix anything, and it shows up when you're trying to finish work. I got some beta trial for Lightroom and that was interesting, but didn't encourage me, as it was extremely buggy.
At some point, I had an offer for Capture One from Phase One, version 2 or 3. I downloaded it, and tried to use it. It was a bit of a pain. However, it produced reasonable results. As the versions have come and gone, the application has become as important as the camera body to me. Version 7 has been on a bumpy road, with the integration of media storage, but it now is easy to use and has produces high image quality, likely second to none.
Their version 7 imaging engine has even given me better quality from older images, at least, with the E-5. Noise doesn't seem to be a factor, unless you're working in really low light. That said, current digital sensors all seem to be better than the best film, and many have come to have a grainy look when they produce a lot of noise toward their limits. That isn't much different than film. (At this point, I don't even need Photoshop, as Capture One does so much, especially with additional Pro version features.)
In any case, I'm sad for all of the Aperture users who will not be getting upgrades. I think it speaks volumes about choosing Apple for applications. Will Final Cut Pro go away? Did they make a deal to keep Adobe applications on (Mac) OS X, killing Aperture? It seemed that Adobe responded very, very quickly to the announcement, as if they already had plans.