A warning: strong opinion on its way! Stand well back - toes might get trodden on.
My definition of sentimentality is emotion looking at itself. My partner Rika says it's like drinking the wine, upchucking it, and then drinking the upchuck. Much of what is called "sentimentality" is emotion - and as some others have said in this thread, what gets to you doesn't get to me, and vice versa. And much is well-aimed and commercial sentimentality.
I've been singing and listening to folk song for thirty years or so (as many of you have, too!) and over the course of that time, I've noticed a change in temperament, from emotion to sentiment. In the folk milieu I like almost nothing made by Bok, Stan Rogers, David Francie or Bogle, finding them all pure treacle. I wish it weren't true, but there's precious little modern stuff I *do* like: when it isn't preachy stuff telling me it's only a wee-wee or I can be whoever I want to be (fine uplifting stuff, taking the place once held by religion), it's fake maritimers telling me that I can rise again, surrounded tho I be by smiling bastards. Thank god I say for traditional song, the sentimentality of which rarely goes further than "The Dark-Eyed Sailor".
Maybe there's more folk who think this, but I'm an old fart who not only bores folk but shocks 'em too with the songs I *do* like (like Child ballads!).
My 2c. Jon Bartlett