With love and respect for others like me who have been using Macs for many years, the simple fact is that once Apple decided to abandon 32-bit architecture in favor of a more robust and capable 64-bit operating system, the only significant change was the abandonment of 32-bit software. The underlying library for Aperture needed updating by the OS and once complete, will do everything you expect it to do. Aperture is no longer available for purchase, but it still works and will continue to do so for as long as you use it. And Photos goes way beyond what iPhoto could go, including support for libraries that exceed 10,000 images, something that's happening now with the use of digital cameras. Not just iPhones, but Nikon, Canon, Pentax, Olympus, Leaf, and more. We capture more moments because the film is free and being able to manage large libraries comes at the small price of adapting to new ways of seeing them.
The observer's comment about buying a new Mac every five years certainly ought to resonate with those whose PCs last for three and will not run the most recent MS OS. My 2008 MacPro and my 2012 MacBook Pro Retina continue to run all of my software except MS Office 2004. Office 2008 and beyond work just fine. FCP 7 and FCP X work beautifully and the only reason I've moved from 7 -> X is that FCP X is faster, easier to control with frame-level accuracy and filled with all the extensible plugins that are available for Premiere.
Oh, one more thing. Apple doesn't charge for its upgrades! The Mac OS upgrades since Snow Leopard have been free and each update of FCP X has been free once you purchase for $299.
Where do MS and Adobe fit in that upgrade price structure?
Apple is very much into helping the customer leverage of their hardware purchases with ongoing upgrades/updates to assure speed, reliability, memory-management, power-management, safety/security, and overall performance. The only price the user pays for these features is the need to adapt.
If you hate adapting to take advantage of these features and more, then stick with the Commodore 64 or Atari, or IBM PC or Peanut running DOS.
This is not a flame; just a statement from an unapologetic Mac-a-holic since February 1984 who left DOS to create and work, not to "tweet the bios" to run faster. And, in the interest of full disclosure, I am an Apple employee who trains people in the integration and use of Apple products and software to enrich their lives and creative endeavors in photography and video. I love helping Windows -> Mac switchers, many in their 50s and 60s and older, discover the magic and hear them say: "I don't know why I waited so long - this is amazing!"
Taylor Swift: "Haters gonna hate."

I just upgraded to Yosemite, apple's new os for my imac. Now my Aperture won't open--says it needs to be upgraded in the App store, which App store says it is no longer available. I sort of understand Apple deciding to deep six a fine program they have decided not to continue to support. But to make it unworkable on the new system seems shortsighted and quite frankly a pain in the pocketbook. I am converting all my aperture files to lightroom, but there are things I would still do in Aperture that are superior to Lightroom. So a warning to all hogs--if you want to continue to use Aperture, don't upgrade to Yosemite---unless I'm missing something.

I just upgraded to Yosemite, apple's new os for my imac. Now my Aperture won't open--says it needs to be upgraded in the App store, which App store says it is no longer available. I sort of understand Apple deciding to deep six a fine program they have decided not to continue to support. But to make it unworkable on the new system seems shortsighted and quite frankly a pain in the pocketbook. I am converting all my aperture files to lightroom, but there are things I would still do in Aperture that are superior to Lightroom. So a warning to all hogs--if you want to continue to use Aperture, don't upgrade to Yosemite---unless I'm missing something.