My biggest regrets about RTW is how they had many things that worked pretty well in MTW, and that work much worse in RTW (the friendly fire is one of the most blatant).
Also, I've find that the AI, the diplomacy, the economy and the public order, were potentially great, but were somehow bad implemented, and this have a vicious tantalous effect (seeing the potential while enduring the flaws).

But the game is still great, the graphics are perhaps not all the game, but they still account for a huge part of the immersion, and many things are simply great.
Additionnally, I don't remember ever crashing to desktop more than once or twice since I've the game (which means : from the very, very beginning).

I await the patch with impatience, and though I don't think it will solve everything, I hope it will fix enough so that the game lives more up to its potential.