FWIW - I have been using the DF500 for about 10 years, I bought one new when they came out. I do love the machine and have built countless things in all shapes and sizes with it but like all tools one has to develop their own usage system. Like some of the others on this thread, I do not like the wide sloppy mortises, I agree with the comment asking why Festool thought they have to be so huge - especially with two sizes, adding a +0.5 mm feature would have been more useful than the +5mm middle sized mortise. For me, the only thing the extra wide mortise is good for is when I cut my own wide tenon for the occasion project that is too narrow for more than one tenon but requires more strength than supplied by the standard loose tenon.

Therefore, I rarely use either of the wider mortises, to me the extra time involved in fitting it all together is worth the extra strength, as another member said, it does depend on the forces exerted onto the joint. The only time I use the wide sloppy mortises is if I am using it more for alignment that may include shear forces but not racking or pulling forces.

I have found the cross stop and mortise pin-alignment system to be useless for cutting multiple mortises - for me personally it causes more trouble than it is worth, thus everything is done with a tape/square onto pencil or a knife (and transferred across the joint at the same time) and cut with the cursor. This pretty much always works with two tenons, but when things do not fit perfectly with 3 or more mortises I often can address that with just a little gentle paring on a tenon with a chisel. For inside projects I also have found that fitting it all together with hide glue is a good way to deal with multiple mortises, the hide glue acts much more like a lubricant than PVA and the longer assembly time allows me to go around the whole project gently tapping with a mallet until I can fit it all together.