I played the blitz way once, and was thoroughly unimpressed. The major tactic seems to be catching the AI early, off gaurd, and forcing them back so they cannot respond or gather enough money to fight back.

As that goes, you end up fighting relatively easy battles, and the AI doesn't put up any sort of challenge.

I prefer to take it slow. I'll fight and scurry to the rebel provinces nearby, but I'm very loathe to break into war with neighbors. It makes me focus more on my agents, and more about what's going on within my borders. Often, if i war with a neighbor, I'll only take a city or two, and often consider returning them to their owner on the signing of a peace treaty.