I think VM's comments are correct about fun and it certainly isn't fun playing the Russians most of the time in these games. It is in fact a very challenging thing to command them and I would say from my experiences usually far more so than playing as an Axis commander.
But it adds insult to injury when you see the Axis getting advantages they didn't get in reality, like the movement rates in the mud issues being discussed here.
I know it's a fine line reality and playability but with computers this should be achievable.
There are comments in this thread that the mud didn't really effect the Axis advance as much as we are like to believe. This is blantantly untrue, there are so many books and films on the subject you have to be blinkered to belive that.
I don't pretend to have the answer to this problem but there really should be something to stop German armoured units running round amok whilst everything else is floundering in the MUD
Cheers Gordon