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Little Snitch interrupted me with an update notice, advertising improved compatibility with OS X 10.10.4. I went over to the App Store to look at updates, and only saw 10.10.3. My audio setup is still on 10.10.1 (it ain't broke and all that). I inadvertently clicked on the 10.10.3 update, and was asked to agree to the terms. I clicked Disagree to cancel it, and it started updating anyway. I cancelled the download, and it stopped, then started the download again and kept asking be to agree to the terms. This kept going on until I logged out. What a weird system this has become.

or

Or perhaps they meant improved compatibility with the upcoming OS X 10.10.4.

Just go ahead and get 10.10.3. I don't think you'll regret it. It seemed to fix an issue I had with the Finder not remembering its window size. The iPhoto thing is a different matter. Seems some can still use iPhoto and some can't, depending on how and when things were upgraded in the App Store. Me? I personally don't hate the Photos App as much as some others, as I always hated iPhoto and struggled to get used to its idiosyncrasies over the years. No, it's not LightRoom or Aperture, but it's perfectly adequate.

Yes, I agree that LS is notifying you that it is tweaked for future upgrades.

I probably will, but I have to get my Aperture lib in shape, backed up, etc, and Aperture running properly on another partition with an earlier OS X version. I played with Photo, and it's fine, but I'm not about to throw 40,000 images at it without a Plan B.