I have used Aperture 3 with Lion and Mountain Lion on a late 2011 MBPro , processing large (45MB) raw files over the last 2 years. When doing multiple edits especialy with multiple masks and brushes Aperture would take moments to process and then move on. This even with an SSD and 16GB memory. Not a problem with little effect on my productivity, processing hundreds of images in a session.
Following Mavericks and Aperture 3.5, Aperture no longer allows more than a handful of images to be processed before it exhibits strange display problems. These comprize of the unzoomed view becoming the zoomed view and this is visible in the preview thumbnail too. It happens most quickly in full screen mode but also less quickly in windowed mode. Simple exiting Aperture and reopening it restores normal functio and edits and previews are correct. A memory meter shows that Aperture decrements memory with every image viewed and doesn't release it, hence i think a memory leak.
I had hoped that the Aperture 3.5.1 update addressing performance issues would solve this. It didn't. I have a crucial SSD self fitted which has worked flawlessly over the last year and have updated Trim enabler after Mavericks which slowed down the leak.
I can't seem to contact Apple support by email as I am not an Applecare subscriber and can't find a way to report a fault without being one.
I have read that there were memory leaks in Aperture 3 years ago and these went away quietly as Apple updated either
OSX or Aperture.
I've not seen others report what I am experiencing, but would welcome feedback from others with knowledge, experience or just bothered by the same problem.