Well, after about 35 hours my Gwined campaign came crashing down all around me and I was wiped off the face of the game world. I was doing well for about 2/3 of the campaign and got very close to my kingdom victory objectives, but I did not play aggressively enough and in the end Welsh rebels, Irish armies, my own royal family and Anglo-Saxon nobles all dined on my Cornwall dragon's corpse.
Both Welsh campaigns are rated as 'hard' and I believe it now, along with JD's claims above that the game can get frenetic towards the end, with the whole map jumping down your throat. All that said...ToB is by far NOT one of the worst Total War games...far from it. I will play again, maybe an Irish or Anglo-Saxon faction. Something not as difficult.
Bastards.