I thought Murder Junkie's description "gimmicky crap" seemed rather fitting
I'll admit I haven't listened much to their later stuff, but it always seemed to me the only reason they got popular was because they, well, covered Metallica on cellos. I guess it gives them some kind of value as a curiosity, especially with Metallica fans, even though their covers sound like crap compared to the real thing (imo). In other words, I don't think they rose to fame on the strength of their music, but rather because they're gimmicky as MJ would put it.