I couldn't help feeling that this episode was very similar to the first Season's "The Unquiet Dead" and Season 2's "Tooth and Claw" and that there is a bit of a pattern devloping there. Nonetheless I thought this was a good solid story.
I think the relationship between Martha and the Doctor is developing nicely, but I really hope that the direction of Martha is different to Rose, as I alway felt Rose and the Doctor had an odd and uncomfortable relationship from the viewer's perspective.
Some of the references were a bit naff, and Shakespeare's constant comments on using the Doctors words was a little contradictory to the fact he was meant to be a genius and also a little repeditive.
I liked the witches and the basis for their power. I wasn't 100% convinced by the Doctor's explanation of their power but I liked the idea, being a bit of a Harry Potter fan myself.
Overall, not too bad. Not as thrilling as "Tooth and Claw" but still interesting.