I am an old timer and use top (instead of Activity Monitor) to keep an eye on my system.

I just notice that in Snow Leopard when you horizontally resize the Terminal (or xterm) window, top displays more information about the running processes -- new columns are added as the window grows wider. Use man top to get an explanation of what those extra columns display.

Another nice change is that the Process ID (PID) is now suffixed with - to indicate a 32-bit process, and a * to indicate a PowerPC process.