We have always known that the Republican Guard would fight back. I don't expect a push against them for several days, until they are severely softened.
Look at it like this - the air war against the Iraqi ground troops has just started. But we have a 250 mile head start. The RG are not only being pounded with B-52s, but also, thanks to our bold advance, artillery and close air support. Seems like a lot better option than just being in an air war, with our troops still in Kuwait and 300 miles of unknown still ahead of us...
I think the war has gone well... on all fronts...