I saw this in the cinema first and as with any movie there are definite do's and don't's.
Don't expect a ten million pound blockbuster with special effects to go with it - there are other comments here about the budget. I've no idea what the film cost to make but clearly it wasn't made on a Hollywood style budget.
And don't expect entirely passive entertainment - script and plot make you work a bit for your money, you've got to keep up, the devil is in following the detail.
Do expect lots of fun, good lines, script twists, a few laughs, great cast with really good performances and a well crafted movie. It's engaging from beginning to end and well worth the watch. Got any more like this back there?