Kingsman tells the story of a kid with wasted potential being recruited into a super secret, non-government run spy agency and obviously ends up trying to help save the world from a crazy megalomaniac. As cliche as I made it sound, this film actually has a very good story and very good action and special FX to back it up. It also has many likable characters - actually pretty much all of them, even the blood / violence phobic villain played by Samuel L. Jackson who does a fantastic job here.
Don't mess with the Kingsmen.
I quite liked the many nods to the other spy flicks too, though the incredibly poor shooting by the generic bad guy minions near the end versus the heroes near perfect aim took it a little bit too far but that's just a minor point. I also love the Maccas advertisement they managed to work into the plot. All up I give this very enjoyable flick four and a half leg blades out of five (Yes, I'm trying to move away from continually using "bullets" :P). Highly, highly recommended and one I'd love to see again!