Slap Up Party: Arad Senki is a rather slow paced, and basic shounen anime. Some things do stand out that I found rather enjoyable.
Story: There isn't much story to be had. The premise revolves around trying to cure kazan's curse, which is responsible for turning people into demons.
Animation: I quite liked the animation. It's colorful and vibrant, and the characters and scenery are just nice to look at. The animation is pretty smooth throughout.
Sound: Nothing really stands out, though I enjoyed the retro goodness of the ED.
Characters: There is not much in terms of progression or back story, but the characters are nicely designed and are rather entertaining. There's Baron, the demon knight, who is a laid back defender of justice. He has some funny moments, and is pretty cool. Next is Capensis, the gunner, who is similar to sanji from one piece, but isn't as cool and is more goofy. There's Ryunmei, the fighter with large breasts. She's your basic independent woman who is the base for light ecchi elements, yet doesn't really get annoying. Then there's Ixia, the young mage. She's generally not very exciting, but has some funny moments. Last is Jeda, the manly, funny priest, who is borderline homosexual. He is quite entertaining and funny, though unfortunately he doesn't get many scenes to show that off.
In conclusion, Slap Up Party: Arad Senki can be a fun little show if you enjoy shounen anime, and do not mind the slow pace and childish overtone of it. I'd recommend it to people that enjoy watching more family friendly shounens.