Fandir nailed it.
I hate having to Wheel, turn, reform or whatever to just get that excact angle to overrun into another enemy (which you then debate with your opponent for 15 minutes).
The other problem is that there are too many movement rules in general! Its not just the movement rate, thats easy enough, but the actions i mentioned before. They are all complicated. How many models kan you swap to the front rank with the expand frontage thing?.
We have to look that up all the time.
When we play 40k we sometimes check the book once to find something really odd or specific wording. When playing fantasy we end up checking the book several times just to check on how the "basic" movement actions actually are!
So those saying the movement is more complicated than 40K might have a point.
I realise 40k has its complicated rules as well but in general i think 40k is easier to learn than fantasy...
Another important thing about 40k vs. fantasy is that you NEVER use the terrain in fantasy! You avoid it like the plauge. Half movement and for what? a minus to hit modifier to the enemy? Shooting isnt even that important in fantasy.
In 40k models are litterally tumble over eachother in the terrain so they can get their precious coversave.
It just gives the whole game another feel. Less static and more dynamic. Some guardsmen running through some craters or basilisks making new ones!
Never use terrain in WFB? Nah, I've often used the terrain, and I mean both tactically and moving in it. Sure there are units I don't tend to have move through terrain more than others, and with the type of combat it represents, this seems to make sense.
Shooting isn't important in WFB? Forgive me, but I'm an Empire player, and if I didn't have those cannons, things might be tough. I'd rather not give up the luxuries of crossbows, handguns, and arrows either.
True, in 40K, models move differently, and thus use terrain the way they do, but this seems to make sense with what the rules system is trying to represent as well.