It's a very good home defense gun - can't go too wrong with an 870. Mine patterns very well with buckshot. Holds 6 in the magazine (for the 7th round you'd need one in the chamber). It has an 18-inch cylinder bore barrel and a perkerized (mat black) finish.
The Mosberg 500-series are a little lighter because they have an aluminum receiver, but I appreciate the weight of my 870 due to the recoil of 12-GA shells.
The 870 is a very proven and reliable weapon, and there's a very large aftermarket for it. Police agencies have used them for decades. The only thing I did with mine was install a side saddle shell holder and a hardened extractor.
If you've never shot a pump shotgun before take it to the range and get used to it. Biggest problem people have is not cycling the slide all the way and jamming the weapon - training issue.
You can also convert it to a hunting gun by changing the barrel and putting a plug in the magazine. (Although I'd rather use my Wingmaster for hunting.)