I have a four year old Laptop. Everything is fine. But Ive put in a SSD and I have 8 gb ram. So besides suggesting upgrading the ram, if the imac will take it, have you looked at all the maintenance suggestions in the FAQ section. Ill mention a few… Disk utilities for Hd, boot in safety mode and then restart, do all three steps in the repair and rebuild AP lib. Make sure you have 80-100 GB free space on the 320 HD. There are others but thats a good start. For a professional photographer shooting alot, those maintenance Items are like a cars oil change.. every 6 months whether you need it or not.
Cheers David

I am with you on this one Jon.

I to have been feeling that aperture has been feeling the strain since changing the OS X version to Mountain Lion.

My mac is a Mac mini with 2.4ghz Dual Core 2 Duo. I have maxed it out on RAM at 8gb, which at the time on Lion made it feel to fly.

I did a clean install of Mountain Lion and my booting of OS X, running of aperture and shutting down of OS X now just makes it feel like the mac is in pain at some points. It is usable just does not feel as zippy as it use to.

I am going to put in a SSD after Christmas to see if that helps out. My Library though it on an external drive on a firewire 800 connection. Although if I run a library on my Mac’s main drive it doesn’t seem to speed it up any.

I have tried a few things like Onyx and CCleaner and nothing seems to make it as quick as the old Snow Leopard and Lion days. I know OS moves on and demand better hardware but I would not thought it would have been that harsh a demand on my mac’s specs.

I run Mountain Lion 10.8.2 and Aperture 3.4.2 on a late 2007 MBP 2.4 Ghz C2D, 4GB RAM and don’t see much difference in performance with my 21.5” iMac, 2.5 Ghz i5 with 12GB RAM … though I use Aperture on the laptop when working outside the studio with much smaller libraries … Given that the laptop drive is only 4800 rpm I think accounts for the difference …

I did a clean install of Mountain Lion and manually installed all my apps as I had a lot of clutter built up from the past decade of pulling over supporting files using Migration Assistant … I’m not sure if that had any impact, but ML seems to be much more stable and responsive than Lion was …