I purchased this in addition to the copper ul4 2011 version. I find the fly to be quite expensive and very flimsy. This, of course, is to save weight; however, the fly appears to possibly not perform under really wet conditions that I have seem yet in this dry year.
That said, the BA system requires the use of a footprint in order to lock into the rain fly. It also is part of the system that makes this tent so strong when fully assembled.
I plan to use a poly tarp under it during times of potential rain and during winter. Redundant but the floor serves a purpose beyond being simply a footprint.