I did and do; when performance at the database level isn't right, you need to look into OS stats, I/O stats, disk stats (the SAN is an area ripe for unexpected contention, RAID5/6 act like a single spindle and inhibit random access in ways that RAID1 or RAID10 don't, stripe length in RAID5/6 bloats the size of small writes, etc.), but I had to stop somewhere :)
So I'm confused - how many years did you have to study before you felt confident enough in your grasp of all the underlying concepts to write your first "Hello World"?