Thankfully, I'm not one of those fans - because I absolutely loved this episode.
Granted, as a "romp", it comes between a rather dark episode (Into the Dalek) and what looks to be another dark episode with Listen. I don't care - this is a flat-out fun episode - the kind of episode where uberfans would whine about "the Doctor wouldn't do that" or complain that this isn't dark enough.
"Richard the Lionheart! Cyrano deBergerac! Errol Flynn!"
On the one hand, if you want to see Robin Hood and the Doctor bicker for 45 minutes - and that's your only standard - you're in for a treat. This is undoubtedly Mark Gatiss' love letter to fun, goofy Who....and there's not much of a subtext. Oh, sure, there's the obligatory reference to the story arc this season - and there are tons of clever lines, way too clever to quote - but this is simply a fun, refreshing take on Who, especially after the sturm und drang of....well, let's just say Season 7B and be done with it.
Is it the greatest Who episode ever done? No. But anyone who hates this episode tends to hate puppies. And Democracy. And should probably rent Errol Flynn in The Adventures of Robin Hood to be able to "get it".
But my personal favorite moment - celebrity cameo!