I do web development, so I have many browsers installed.
The tests below were done trying to load
www.google.com and
www.yahoo.com
Chrome (2.0.172.30), Opera (9.64), and Safari (3.2.3) took approximately 2-3 seconds to load.
Firefox (3.0.10) took approximately 3-4 seconds to load.
IE (8.0.6001.18762IC) took between 14-17 seconds to load.
I also loaded the blank page about:blank onto IE8 with no appreciable difference.
I disabled all addons through Internet Options in the control panel and also saw no change, I then reenabled them.
I saw this thread and disabled SDHelper and saw no change.
I then went into immunizations and removed all immunizations for 32 and 64 bit IE and saw a massive change. IE now loads in 4-5 seconds. I re-enabled the immunizations and again it slowed down to 16 seconds (only tried it once) and then disabled them, again the startup time went to 4-5 seconds.
I'm using an HP DV9930us Notebook with Vista Home Premium 4G RAM and Intel Core2 duo at 2.00Ghz (x2)
I only really use IE for web development, Firefox is actually my main browser (still has it's immunizations along with opera and the hosts file), so it won't hurt for me to have the immunizations disabled for one of my browsers. In case anyone stumbled across this thread though, maybe this will be of some assistance in pinpointing some issues.
Edit:
I forgot to add, i'm using Spybot 1.6.2.46