I actually started watching this as part of my fluff Saturday viewing (where I watch shows that really don't treat their situations and environment as a true drama should), and it has a bit of charm and I do love the banter between Arthur and Merlin and Morgana and Arthur. But I do wish to see it keep those elements but have a bit more drama to it.
I hope there's a second series- the show does walk the line between good and crap sometimes, but like all good shows it works because it's well cast. As stated the interplay between Merlin and Arthur especially works brilliantly. As an aside I love the CIN bit with Anthony Stewart Head "Give money to Pudsey, or I'll chop your head off."