I like the style of this episode and the series in general is taking. It has a mysteric athmosphere, and I think that is what they're trying to create.
If I recall it well, this is the episode where Poirot says "Mademoiselle, something ...". He said it so quickly, that I heard "Mademoiselle Something". I am not sure if they did that on purpose, or not, but for me it was a comic moment.
They do try to add humor to the series, in a way without of course turning it into a comedy.
Unfortunately they failed with miss Marple, the new one just isn't cast right !
David Suchet has done what Jeremy Brett has done with Holmes (eventhough I wonder what Downey Jr. will make of it), they are the personification of the character in the books, excellent casting was done for these 2.
The last 2 seasons were already excellent, not just a TV-series, no, they're now making 4 movies per year, since they have that quality.