Well, since there isn't a review yet, might as well make a quick one.
This is just another episode, which is good stuff. More impossible tasks for our characters to try and figure out! But yeah I mean. If you watched the main series and enjoyed it, this is just an extra episode. There isn't much more to say really.
If you haven't watched the show yet, you could potentially watch this still and give it a chance. You may not know each characters quirks, but you could possibly figure a bit out about each character through this, and then decide if you want to watch the main series.
But yeah, that's about it really.