Fight Night: Champion's demo arrives Tuesday, but apparently some in the UK have gotten their hands on it. Notably, the demo will include online multiplayer. This series of videos gives you a look at what to expect from it.
My early impressions are that the graphics are strong and the punches come in quicker, tighter, and with a lot more pop. The game's stamina overhaul, however, is not really evident in these four videos. Boxing's biggest problem in a video game is punch-spamming without penalty and it doesn't appear that many are paying the price for doing so.
That said, the demo only gives you three round fights, so the long-term effects of stamina drain may not be evident in any aspect of the demo. The inclusion of online multiplayer makes the demo worth checking out by itself to me. The main game will arrive a month later, on March 1.