As you see, two-pane as being an Inbox with a list of recently arrived emails, and then the ability to tap on the message split the pane in two in order to read the first few lines of the message at the same time your main Inbox UI stays open.
Admit it. You can do this in Outlook Express, Eudora, Incredimail, Thunderbird, almost every other every other desktop centric email client. Would be a nice feature to have on your iPhone, no?
But as Ryan show us and some of us now realize, there's no double-pane in the iPhone's email inbox.
OK, I'll spare you the "one-pane, no gain" pun. (Well, I guess I didn't, but my pun-banning girlfriend is out of town for the weekend w/out her laptop, heh).
My next question would be to ask you if you wish there were two panes.