Opera is better than IE, since version 4 i guess . Now Version 9 is in preview. I tested it. Of course, my opinion is influenced by cool browsers like Firefox or lynx.

Actually, Opera isn’t a browser as well as Google ain’t a search engine. So I have to split my testing.

• Software reacts really fast.
• It looks good by default.
• Skins are applied in realtime. (in contrast to Firefox, Thunderbird)

• NT-Auth doesn’t work? It did in version 7/8.
• Site Preferences are way too detailed
  

You can configure, how a site, e.g. google.com is treated (images, js, popups, cookies, ...)

• You can’t resize the AJAX Widgets.
• Some pages look very strange, like http://my.opera.com/community/contact/myopera/?selected=feedback

• Block content is user friendly
• The AJAX Widgets are totally cool! (always on top, moveable)

• The arguments of Opera (Tabbed browsing, Security, Searching, Skins, Zooming Images) are nothing special (except for IE-people) and should be standard.
• Firefox with Mouse gestures + Adblock + a Skin + Fasterfox + a cookie manager is faster and better (except maybe for the AJAX widgets)

• leaves messages on server by default (in contrast to Thunderbird)

• Couldn’t connect? And doesn’t show a message why?

I stopped testing at this point.

• NT-Auth doesn’t work.
• Mail (POP3 download connecting) didn’t work.
• Widgets can’t be resized.
• You can look through the border of drop down lists to the window below.
  
• On their own pages, they say “We see that you are using Internet Explorer.” when using Opera 9.

Might be that this preview is a little buggy. I’ll stick to Firefox and Thunderbird for the moment. (and don’t forget wget!)