My experience is that it's almost always better to wait. Except for really HUGE games, tix prices decline as the event draws nearer and sellers get more desperate. Stub hub actually offers a program that reduces the price as the game nears automatically when you sell tix there.
Here is a side question since so many people have posted about tickets. Are you finiding stubhub prices to drop dramatically day of/day before?
I have a friend coming into town next Friday and she wants to go to the game so I'm curious as to whether I'm better off waiting. I will probably have to wait until Monday at least anyway.
Also, I would recommend checking at fansnap.com before buying on Stub Hub or Ace. That site aggregates many of the on line brokers, including Stub Hub and Ace, so if there is a deal out there to be had, you wont miss it.