I don't know about the resource hog, playing with Counters slows my game down just as much. I think the major issue is that the game "grows" constantly: more IC built, more and more units and once the war breaks out: more and more combat. Now, I think the EU3 engine can handle a bigger load then the old EU2 one, but EU3 has the advantage that the number of troops decreases after war, in HOI they all stay. Also, some better coding might solve some issues.
Anyway, from Twitter: "Of course, it is very important to have unique cavalry sprites for most nations."
I sense a hint of sarcasm, but at least I think we'll have cavalry sprites! Huzzah!