Hello,
I have just used the 365 drill bits for the first time on a job with very hard full bodied porcelain tiles and they worked superbly.
The hole sizes ranged from 8mm to 50mm in fixed and un-fixed tiles and every hole was spot on, even when cutting crescents from the edges of tiles. The 8mm bit has cut 24 holes now and it's still going strong!
The only problem I encountered (as others have experienced) is that the yellow guide plate wears after only a few holes. I ended up drilling a whole load of other 8mm holes in it and used them.
All in all a great product
Mark