One night in bad weather, in a good tent, will convince you that every cent you spent on it was well spent.
I don't use a ground cloth, but carry a foam pad and a Sea to Summit inflatable mattress. I concur with Indyfab that it is terrific. My hope is that the foam pad will reduce wear on the tent bottom. I have a NEMO Hornet which is nominally two person, but I like the room, and being able to get everything in out of the rain.