Do you use Exchange with Mail.app? I was very happy that it auto configured but if it is to crash while sending email and does NOT have the courtesy to restart and restore the email - it is POS. I have already lost one long email initially after the crash - it just vanishes.
Mine is a MBP2,2 - Core2 2.33Ghz with 3Gb RAM (Refurbished - so it is not even a year old - still under warranty) and no crazy applications that load kexts or anything - just stock Leopard install with FireFox, Office 2008, Skype etc. I had no crashes or any troubles with Leopard.
Battery life definitely went south - it's not just that it is reporting less, it actually is less. Very bad.