ITA about 510 but it wasn't much problem for me to leap from comedy of 509 to drama of 510 because for me the season contained less eps than was shown and after 504 (with gag reel as 508) i count the next ep as 510 so for me there was continuity with drama :)

I really liked 209 of Merlin because of so sweet Merlin-Arthur scenes. Didn't bother aboout storyline though.
As for 210 i expected worse, a lot worse. Gwen totally annoyed me there but i ignored her and watched for comedy of 'Artur in love' and (again) for nice Merlin-Arthur scenes.

The preview for the next ep looks intriguing but i'm sad they'll make Morgana bad (i know it's classic but still...)