I spent weeks looking for this answer, and then pissed off a few people trying to aggressively get answers... sorry man, it is not possible (or at least, it wasn't a month ago). However, I think New Sense is supposed to allow for home screen rotation.

FYI, what I do: I use Sense all the time, EXCEPT I have a Tasker profile setup so that when I get in my car and put the phone in the mount and plug in my charger, Tasker launches Launcher Pro for me. It gives me that screen rotation, as well as the ability to have that custom home screen setup with more "driver friendly" shortcuts than I have on my normal homescreen (wifi tether, google maps, etc).

Then when I unplug the charger, it automatically sends my phone back to my regular Sense desktop. It's not as good as if the homescreen would just rotate automatically IMO. But at least I'm not stuck running LP all the time, and I get screen rotation when it really matters.

 

The only problem with having The screen autorotate, like with LP, is that when you take it out (of say your pocket) to answer a call, or text, it rotates to landscape and you have to wait for it to rotate back. Kind of annoying.

 

I figure I will bump this thread rather than start a new one.

I just saw the commercial for the Evo 4G Shift and it appears as though it has the capability of a landscape home screen. That obviously means it is possible, now how do I get it on my phone? I imagine the developers need to write it in to their ROMs? I would love me some Myn's + Landscape homescreen.