The cast IS great. You may find the first series a bit odd, as it is somewhere halfway between a more-or-less serious medieval drama and the comedy that the later series would become. It has its moments, but it's generally the weakest of the four. Series two through four are all awesome, though, not in the least thanks to Fry and Laurie (in series two, Fry is a recurring character and Laurie has a few smaller roles, in series three it's the other way around, and in series four they both appear in every episode I think). The others are short specials, which also definitely have their moments.