The Remington "Security" is an 870 variant. It has a shorter barrel (18" I believe) and a 8-shot tube. It can fire 2 3/4 and 3" shells, but is not rated for Magnum loads. You can shoot anything through it except rifled slugs.
The receiver is a standard 870 receiver. The barrel is a littl eon the cheap side, because it's not designed for the heavy use and abuse of hunting or trap/skeet shooting. It's designed for DEFENSE--meaning it's not designed to shoot all the time.
But it IS a Remington 870, which means it should be a good gun. You can probably get a better price on it though. Shop around.
Look at the Mossberg 500 "Field/Security Combo" model (#54169). I got one with wood furniture, and it came with an 18.5" AND a 28" vent-rib, ported barrel so I can use it for hunting/sporting and defense. And if you want it REALLY short, it also comes with a factory pistol grip (polymer). It has a 6-round tube though, so it's only a 6+1 shotgun, and the Mossberg design requires replacing the barrel if I want to install a longer magazine tube. But I think that 7 rounds of 12ga are probably about 6 more than most folks are going to need in a typical home-defense situation...
http://www.mossberg.com/products/default.asp?id=3&display=specs
I got it for a tad over $300, and it is a VERY nice gun. Two barrels, smooth action, and the wood furniture helps keep the "tacticool" factor low in case I ever have to face a hostile DA. And since it sits in the house most of the time (or is only on the range outside when the weather is nice, for shooting "5-Stand"...) the wood furniture is holding up perfectly.
You might also check out Gunbroker.com. You can get some FANTASTIC deals there--even with the shipping and transfer fees added on...