I think the game is finally what what it should have been at release, if not slightly bettter. With patch 9, the campaign AI is good if not great (diplomacy is the best of any TW game thus far IMO).
The battle AI is decent. It tends to do well in regular battles and non-walled seiges. It is ok when it comes to walled sieges. Sometimes it acts intelligently, and much less frequently does it act stupidly than before. I'd say seiges are no longer broken, but not quite ideal yet. Thankfully there is at least one more patch due soon.
Some of the major MP problems have been fixed, but they are (presumably) still working on the rest.
If you're a fan of the TW series, definitely give it a go at this point. Mods also can really improve the experience. I'd say that with mods, its quite a good game as of now.
Too bad they really botched the release. It irreparably hurt the player base and franchise reputation.