Have you looked at Outlook 2010. They have a similar conversation view. Outlook also gives you the ability to respond to mail with a phone call (Google must have this capability with Google Voice, but don't see it).
Another feature I like with Outlook 2010 is to see all correspondence from the person I'm currently looking at (email, meeting invites, chats, etc...).
There's also this cool thing called Quick Steps, where you can construct macros in Outlook. This is useful when you need to have specific workflow around email that you can put together in one click (like, when responding to legal, I need to send the reply, delete the original email, send another email to my manager, and send a note to OneNote).
And of course Outlook has a webclient, so I can access it from anywhere too. While Outlook is heavyweight, feature-wise, its pretty complete, and offers some other things that are hard to beat.
Another feature I like with Outlook 2010 is to see all correspondence from the person I'm currently looking at (email, meeting invites, chats, etc...).
There's also this cool thing called Quick Steps, where you can construct macros in Outlook. This is useful when you need to have specific workflow around email that you can put together in one click (like, when responding to legal, I need to send the reply, delete the original email, send another email to my manager, and send a note to OneNote).
And of course Outlook has a webclient, so I can access it from anywhere too. While Outlook is heavyweight, feature-wise, its pretty complete, and offers some other things that are hard to beat.