Plenty of threads on the subject Idris if you care to search....

It's just one of those topics that crops up every 3 weeks or so

Thus far though, I've never been @rsed to contribute, so here's my two pennorth..
Pro's:
1. Errr... it sinks. But don't be fooled by lighter stuff... it still floats like anything else, and needs a helping hand through the surface tension.
2. Stiff. Has it's benefits for droppers/presentation
3. Low refractive index.
Supposedly more or less invisible in water.
Cons:
1. Expensive. Needlessly. We are all being taken for suckers. Me included
2. Stiff. You'll need a low breaking strain Fluoro if you want your flies to 'articulate' at all.
3. Kinks... as soon as you look at it

Kinks can usually be removed by pulling through a rubber pad... careful with that pad though Eugene.. don't wanna 'burn' it now do we?
4. Legend has it that one has to be careful with knots. I just chuck any old granny knot on the stuff though and it's always been fine