Rizmod

I've had MTEC front and back grooved & dimpled discs with the coating for a couple of years now - bought for looks, not performance, but they stop really well in the dry and wet.  The hubs and internal vents haven't rusted.  The coating obviously wears off where the pads rub almost immediately ... and afterwards the discs readily rust there when washed, just like normal discs. I have a little rust staining either side of the pad area as well but nothing like I've seen on previous discs.
 
I don't get ANY noise from either set of brakes using standard Pagid pads.  However, it's easy to fit the discs the wrong way so that the spiral pattern is opposite rotation direction so follow the directions carefully (I didn't and it was noisy for 5 minutes on my test run until I realised and swapped the discs round)!  Also need to put copper grease on the back of the pads (never on the friction material) to prevent chatter.

Stu, I've used a hockey puck with a groove in it for the last 2 years and done no damage to the sills.  It just spreads the load either side of the sill seam (but mainly on the inside as Denis said).  You need the groove deep enough to clear it but that's all.  The rubber moulds itself a bit when compressed.  When I ordered my puck, I had to hacksaw the groove myself, so can't really say if yours is ok.