I think they have a lot to offer especially if you have an 870, just not enough for me to buy one. I've handled and shot a few. My brother had one for a while. They are a better option than a tradional lever action in that they are about the same weight, shoot faster, are more accurate, load and unload easier and are generally more reliable than a lever. Not to mention come in better chamberings.
Accuracy is better than average if you can get past the poor triggers. They are simply not in the same league as a good bolt rifle however. They are on the heavy side and they aren't quite as accuate or reliable. If getting off fast repeat shots are your primary goal only a semi is faster,and they do seem to be a bit more accurate and reliable than most semi auto's.