It's quite a lot of fun. Got a few niggles with it myself, too, though. I'll only mention ones I haven't spotted anyone else saying, though
1. Siege weaponry. Why bother? A unit of Ballistae can easily take down enough of the wall to render a battering ram, siege tower or set of ladders a waste of time and men.
2. Allied AI doesn't seem to understand why stationing its' dignitaries in territories controlled solely by me pisses me off and gets them assassinated.
3. I'm only playing on Normal (I thought the AI'd be normal. Not imbecilic), but the AI's tactic in defending minor settlements seems to be to stand in plain view and watch the Ballistae/Onagers I now have in every army bombard them. Then stand still and watch my slingers kill off the rest of them. Might be changed in higher difficulties, I'm too lazy to switch difficulties atm.
4. Siege AI. They'll charge straight ahead into my ambushes, through the gates with the boiling oil, etc etc. I've won far too many defensive battles due to the AI being too stupid to scout out city squares before sending all their melee infantry in there. Possibly invalidated by me playing on normal, though.
5. I really wish my units would stick to their orders. I don't damn well care if you clipped a single spearman from that unit as you ran past, Cavalry, stopping to fight them all is not what you were told to do, and it'll just waste your lives.
6. Sea battles. I see all these awesome Fire Pot Dieres, Tower Hemiolias, Ballistae Triremes, and my best boat is... a large raider with a bunch of painted nutjobs on it. Greaaat. I want to hurl pots of explosive at people, I mean there's even briton artillery boats in the encyclopaedia. But upon investigation, said encyclopaedia doesn't actually say anything about how I can get a boat that hurls rocks at other boats. Bluh.
3 and 4 are possibly just because I'm playing at too low a difficulty, I suppose.
Even with all that, though, I'm still enjoying it. Currently gets a 6.5/10 from me, and I'm hoping it'll get better as it's patched.
Oh, and the landship bug was hilarious. Only got it once, but having my entire garrison butchered was a small price to pay to see that.