Okay, I’m on the ‘mac’ (specifically, my better half’s ibook). And I’ve switched back to using Firefox on her laptop instead of Safari - since Safari keeps crashing!
Secondly, I’ve reinstalled Opera 9 on my work Windows laptop to give it a go - after spending the last few weeks as IE as my default browser.
I switched from Firefox 1.5 to IE 7 in order to give IE 7 a fair assessment, and on balance, to be entirely honest… I’m disappointed.
Firstly, it is certainly no more efficient than Firefox, browsing sessions with a few tabs open regularly allocate more than 100MB of memory.
Secondly, its popup blocking SUCKS… it seems to block the popups you want, and allow the ones you don’t and what’s worse is its ‘blocked content’ warning seems to constantly interfere with browsing, and even after you allow the blocked content for a given site, it seems to keep warning you about it. File downloading is also less than optimal, I never realised how used to the Download manager window in Firefox I have become.
And the other day, I had a curious error, IE INSISTED on returning a 404 File Not Found error for a particular website, despite refreshing and Shift-Refreshing, yet the site was there and Opera happily returned pages.
All in all IE7 is a disappointment that only just makes the level of functionality that has been in Firefox and Opera for years - and does so much less convincingly.
Don’t believe me, go download it yourself!
In its defence, there are some good bits, the RSS integration is HEAPS better than Firefox (Particularly when you combine it with Office 2007 beta 2) and… well.. umm… that’s about it 
I’ll try and think of something else when I’m using it