Great comment. But I am stuck with Excel 2004 due to it having macro support. I have also stuck with Word 2004 due to its less ill-conceived interface.
I don't suppose running all this ***** software helps but SL doesn't seem to thrive with lots of apps open like Leopard did. I have to restart a lot. I bought a new battery because I thought my 18 month old one was dying but I get almost the same time from my new one. 1.5 h is not enough.
I'm not sure where issues with running multiple apps comes in...
It's practically the same OS. My iMac runs many apps at once. I have two users logged in most of the time with roughly 20 things going at once. Never once crashed. I only reboot when I install a software update that requires it.
SL has different hardware requirements. Install Leopard on a computer that came with 10.3 (would be a .2 jump like Tiger to SL is) and you'll probably notice some issues.
When updating an OS you'll definitely notice driver issues. The OS is going to come bundled with the drivers that are more or less current and that the company thinks people will be using. Apple cannot include every driver ever made by every company in their OS release. If the driver isn't included because you're using an older device, you may have to hunt it down.
Simple.