This was an okay popcorn movie. Bela Lugosi does a great job as the mad scientist in the film. The special effects weren't all that great (the bat looks like an unmoving piece of plastic for most of the film), but it's understandable considering the time period it came from.
The one thing I enjoyed most was how Bela Lugosi always emphasized his "goodbyes" to unknowing people he had marked for being attacked by the bat. It was a very memorable, cunning double entendre that was entertaining every time he said it.
Overall a good old-timey flick. Not necessarily memorable by any stretch, and certainly nothing complex or thought-provoking, but entertaining all the same.