I use CMT 5mm, 6mm, 8mm, 10mm, and 14mm cutter in my domino XL (with the Seneca adapter for the two smallest).  I broke the 14mm the first time I used it but it was rapidly replaced under warranty and the replacement has had no issues at all.  I have not yet purchased any tenons so I have no direct experience with Festool tenons fitting into CMT cutter made mortises but I would not be afraid to try it.  The cutters measure the correct size and so do the mortises. 

I've used all these cutters fairly extensively in the year or so I've owned them.  I just finished a cabinet with 10 drawers, for instance, that are all fastened together with 5mm dominos.  I made the tenon stock out of scraps I had laying around.  I made 14mm mortises for a crib I made so I could make wide tenons on the ends of the plywood stretchers the plans called for.  I made 3 inch wide tenons in a cherry bed I made.  I use festool size tenons in drawers and for some other things (like two small flat panel drawers I made Saturday) but for a lot of furniture I like to use much wider tenons which I made, normally out of offcuts of the same wood as the rest of the piece.  It saves money, makes for a stronger product, and saves space in my shop.