The arbor is the same as the Festool TS55, you can use festool blades and 3rd parties.
I honestly believe that is quieter than the TS55, but I will test that tomorrow and I'll post it. I just got the machine, so I don't konw how long will last, it cuts without chipping and it is very smooth, more than the TS55.
Only you can decide if it is worth it or not. It is to me. I am moving out of state so I will sell all my big tools. I need to replace them with equivalents (smaller size), for the Table saw, I am getting the Mafell Erika. It is very expensive so I will be without the table saw for a while. I need my track saw with enough power and easy to use, that is why I am replacing the TS55. In other words, based on my needs it is worth it. I won't have to buy the TS75 and have 2 saws (75 and 55) to do what my MT55 can do. The difference will be the depth of cut, but I can live with that.
Believe me, the TS55 is a great saw, you won't get disappointed at all, but If you want to go the next step like me then the MT55 fits right.