I just got an email from UW that I am on the waiting list. They said, "All I can tell you is that you are on it and we consider you to be very well qualified for our program." Did you get the same email?
I also got an offer from other program, but I will wait for UW's decision even though it takes a while because it's worth it. UW's program is very strong and attractive. I recommend you not to accept UW-Madison's offer in a hurry and to wait until April 15th.