I am big fan of GMail conversation view as I can see the history of related emails without any problems. How many times I though that Outlook should have similar functionality. However, if you don't like it you can switch it off.
This is what Gmail opinion about it.
"It turns out not everyone feels the same way. And just as an outspoken minority has banded together in unison to declare their distaste of one of nature’s most delicious herbs, some of you have been very vocal about your dislike of conversation threading. So just like you can order your baja fish tacos without cilantro, you can now get Gmail served up sans conversation view. Go to the main Settings page, look for the “Conversation View” section, select the option to turn it off, and save changes. If you change your mind, you can always go back."
Turn off Gmail’s conversation view - Official Gmail Blog
Thursday, September 30, 2010
