Well, F is what you are supposed to use. ESDF is ESDF for a reason – once you get used to it, it’s very convenient to have all the action buttons close by.
It’s the same control scheme used for Lost Vikings, which I played first, and I too started off by using Spacebar, until I figured out that it is actually holding me back, and switched over to F. By the time I got to Blackthorne, it was ESDF all the way. 🙂
Which is why I hate that the updated Blizzard release makes you use both.