I think that was pretty much the best episode so far. Of course, it had to be considering they'd been delaying all this story development so they could show it in the season finale.
Anyway, it did have it's predictable Smallvillesque moments like Arthur conveniently getting knocked out until Merlin finished having his convo with the dragon, but it was still really good. Colin Morgan showed an amazing range, I think (more than the show deserves, really). And... well he was totally adorable at moments as well.
Also very good visually. I liked the bit when Arthur's knights stood around him, forming a "round table", even if they did all end up dying. Yup, I'm pretty sure Will's had his chips.
I wonder what the "story arc" will be next season? Morgana breeding dissent against Uther, I suppose. Except the show would kind of be over if Arthur became king and everything was happy.