I bought Scared Shrekless from a supermarket because at the time the Region 2-PAL version was not available on Amazon UK. Well, now I see that it is, so here's my take on it.
The first thing you need to know is how short it is - just 24 minutes, and I think that includes the end credits. There's virtually nothing else on the DVD other than the film itself, just trailers for two other films (Kung Fu Panda 2 & the forthcoming Puss in Boots) and the stage musical Shrek. Subtitles English only. No extras at all - the 'Thriller Night' shown on the US-NTSC version is not included, whatever it is. It's tempting to suggest that the US import might be better value, then, but as I haven't seen it I can't be sure.
Basically it's a collection of (obviously) short stories designed to scare Shrek, as told by the likes of Donkey, the Gingerbread Man and Pinocchio. Shrek himself doesn't feature much. The quality of the animation is excellent and on a par with anything that has gone before in this series. The stories are loosely based on classic films such as Bride of Frankenstein, Psycho and The Exorcist.
It's funny and had the children laughing throughout. It's just so........short! There's nothing to complain about what you get, it's simply that there isn't very much of it and as soon as it ends the children are likely to look at each other and go "Oh. That was quick". It's not exactly brand-new either, being released in the US in 2010 (i.e. about a year earlier) but only just becoming available in the UK in October 2011 for the first time.
We've got all the full-length Shrek films on DVD and each one has been watched a zillion times. This cut-down variant won't be watched that often, I feel. For die-hard Shrek fans only, I'd say.