Jeremy Scheider's recent post about db_file_multiblock_read_count, a great read in itself, linked me to piece that Jonathan Lewis wrote for Oracle's website entitled "Understanding System Statistics."
Definitely a must-read for anyone taking charge of a 9i or 10g system. I found myself needing to gather system stats again after migrating my database over to a new ZOMG DUAL CORE 64-BIT machine. The numbers were a bit more impressive than the system stats on the old hardware, to say the least. Let's hope that observed performance is equally impressive!