The differance between CMx1 and "CM"x2.

[PoorOldSpike]

you will find that this game is a clunky mess and you will be frustrated in your attempts to carry out your tactical plans.

Yes that uncertainty is a refreshing change and is actually part of the appeal for me.. :)
I mean, in old CM everything can be plotted with neat surgical precision, but in SF it can't, which adds to the challenge.
I kinda like ordering units in SF to "go here, go there, kill, don't kill", and hope they'll perform reasonably well within that framework of orders, so in that respect it's far more realistic than old CM..

PS - and realtime play in SF makes a refreshing change too, as it adds to the realism..
I still like old CM best though, but SF makes an interesting diversion with lots of new toys to play with like missiles and stuff..