I typically do use a groundcloth.  The floor of any tent usually takes the most abuse, so I prefer to to protect my investment:  not only to prevent holes in the tent floor, but also from objects that might damage gear inside the tent (mainly inflatable sleeping pads).  For my car camping tent, it's a big generic tarp.  For backpacking, I have one manufacturers footprint for one of my tents, and a piece of tyvek for the other.  I prefer to accept the few extra ounces & hassle for some modest protection of my gear.