There are a number of launchers that support landscape mode, and personally I like the very simple one they made for the Pro1 (not pro1X) the best, as I like the (IMHO) ingenious idea of splitting the roughly 2:1 desktop in halves and rotate them individually, that is left<->top and right<->bottom with minimal stretch or compression of the icons.
The flip-side of the split approach is that you can not have a widget spanning that centre line, and if you got a large widget, that could make it useless.
A few launchers offers completely independent layouts for landscape and por