If you fill up all the slots on your motherboard, that's how it will slow it down. Almost all motherboards will downclock the memory if all the slots are filled (on 3x or more slot configurations). So it's a waste there. 2GB sticks of RAM are a waste because they usually loose speed at more than 1 GB per stick.
Someone asked about 4 GB sticks of RAM. Yes, there are certain ones, and they really only got used in the PowerMac G5, and some servers. They are available on newegg, with the title "Approved for use in PowerMac G5", but they will work in any mobo that supports 4 GB sticks.
Doesn't anyone remember that you must have a 64 bit OS to use more than 4 GB of memory. I'm not sure if 32 bit OSes will start or not, but I know they cannot properly adress more than 4 GB of RAM.
8 GB will definitely become a standard, not in VISTA's lifetime, not in any lifetime that still offers backwards compatability. So long as the OS still ships in 32 bit forms, high memory usage will not occur even in the 64 bit version of the OS. However, VISTA should use at least a gig of ram. It's about time, Macs and even linux (commercial distros) started requiring more from machines, I want to see a Windows that can utilize better hardware, instead of holding me back to maintain backwards compatability. I think Windows Blackcomb is where we may start to see substancial memory amounts being ulitized.
