I have a somewhat older iMAC with a 3.06GHz Intel Core 2 Duo processor and 4GB Memory, and it's about 2 years old. I'm only about 1/2 full on my disk. I recently "upgraded" to Lion, after enjoying great performance with Snow Leopard. However, my experience has been tainted dramatically with Lion. The first thing I noticed was how slow the system responded just to do simple things like open up a Finder window. Most applications won't open without the spinning beach ball, and open a good 2-10 seconds slower than with Snow. MDS (spotlight process) was constantly running taking up well over 50% of the CPU even a month after install (and the computer stays on pretty much 24x7, and is idle most of the day). I ended up finally having to use a utility to turn off spolight because it was so invasive. One thing that DID help, however, was to remember to start Lion in 32 bit mode. Lion is not like Snow. The default starting mode is 64-bit, not 32. So you must hold down the 3 and 2 while booting. This helped with performance rather dramatically, but I'm still pretty annoyed. I would suggest to those of you that DON'T have the Core 2 Duo proessors, DONT upgrade to Lion. There aren't THAT many features that are worth the downgrade in performance. I've posted this in the Apple Forums and received little response, so if any of you have found tricks tha speed performance in 64 bit more, please feel free to post them here! Thanks.