I haven't been completely content with the 2x2 GB Kingston Apple RAM in my Penryn 2.5 Ghz. Here's a couple of things I've experienced: 1) First time when I ran iWork '08 and wanted to see the introduction vid, the screen froze at that initial screen with an Apple logo that showed up when iWork intro vid got started. After this happened I switched the 2x2 GB I had just installed that morning and put the one above into the bottom slot, and vice versa. After that I ran the Apple Hardware test - both the short and the long one, got no problems whatsoever. 2) At times I get the feeling that the MBP is a bit slower on applications - the spinning rainbow-color ball shows up for several seconds. (for example, if I open several tabs in Firefox and one or more of these tabs got a lot to load on that site) 3) Just today it happened twice that the screen sort of froze for like 10 secs. I played iTunes, had MSN on, browsed online, and when I clicked the orange button (-) on browser and the whole window slipped onto the dock, just before it actually finally disappeared onto the dock, the image of the browser window actually remained above dock for like 10 secs (imagine how an item looks just before it finally disappears down onto the dock) - it just wouldn't budge, and wherever I moved the mouse, nothing would happen. And then after this short lag, everything would be fine again. It happened to me twice today. Could this be faulty RAM?