Uh-oh, perhaps SmarterMail is innocent..
Steve Schofield at ORCS Web just pointed me to a very worrying article:
Why Outlook 2007 is slow: Microsoft’s official answer
My personal PST is 2.6gb.
I am going to SHIT A BRICK if this is true - can Outlook 2007 really be worse than 2003 with large amounts of email?