I must say, my experiences with the strategic AI have been pretty good so far. As Austria on VH/H, I have seen the AI:
*Send multiple raiding parties to raid my economic buildings, playing havoc with my economy.
*When making frontal attacks against my cities, attacking decisively and in strength.
*Best of all, sending a small but capable expeditionary force to bypass my large army in Warsaw and drive straight into my homelands, taking Pressburg and besieging Vienna before I could respond, forcing me into a nail-biting battle to save the city.

If I had lost Vienna, I suspect I might actually have lost the campaign, something I can't remember ever being in danger of in Rome or M2. Perhaps I have just been lucky, but in my experience the AI has seemed to act with a clear sense of purpose (either economic raiding or going all-out to take a province) and always acting decisively and with enough troops to do the job.

Of course, as Austria the lack of naval invasions isn't exactly a major factor; but I'm certainly not seeing anything resembling the confused, dithering AI of Rome or M2. The only problems I have with it are the irritating diplomacy spam (which is making me consider war against Spain and Prussia just to shut them up), and the fact that when I do bring the enemy to battle, they seem to always fight to the death even when they ought to withdraw (e.g. lone cavalry units deep in my territory, having already succeeded in raiding my farms, will then attempt to take on a full stack of my troops.)