Responding to what I can here. I have an 1100M which is the same base machine as the MX with the notable exclusion of servo motors and the bt30 spindle taper. My machine easily holds ±.005" without me having to do anything. I've gotten better and I know many people are routinely capable of ±.001" but that does take more knowledge and skill than I have. For reference, I've been machining running my machine since November of last year and come from 0 machining or CNC background so I am absolutely the limiting factor in my machine's performance.
I have done a lot with aluminum with great success and have have excellent results with delrin as well. I've been struggling with steel but I've done very little with it and have just been using whatever random tools I can find so again, I'm the limiting factor, not the machine. Many here have posted good results with steel in various grades.
Chip containment on the 1100 line is very good. I get the occasional fine chip falling out the back through the gap under the electrical enclosure but it's rare. Out of several hundred pounds of chips that I've made, I think I have a few grams that have escaped the enclosure. More come out when I'm blowing off the table with my air nozzle than escape during machining. I have not yet added a coolant wand but it is on my short list of upgrades. Clearing chips out of the enclosure is a bit of an annoyance. There simply isn't enough coolant flow to properly wash them down the tray and into the coolant tank catch pan. That said, whenever I top off the coolant, I pour it from the edges of the tray and everything washes down fine so a hose run off the coolant pump would definitely make cleanup easier. The other cleanup mod I am planning is a filter bag or similar to catch more of the fines before they make it into the tank. I have already added a canister filter to the coolant line on the back of the machine to catch fines before they make it back to the nozzles and that is working well but I suspect I'm building up a layer in the bottom of my tank that will have to be cleaned out at some point.
I use the 3/4" shear hog and it's great for chewing large quantities of aluminum very quickly. The resulting surface finish sucks but it's a rougher so that's to be expected. I also use the superfly and have had excellent results in aluminum. I have also used the superfly on steel (different insert) and that worked well and gave me a nice surface finish.
I haven't had my machine that long, nor do I tend to run it for more than a couple hours at a time but I've yet to notice any issues with pathpilot slowing down or becoming less responsive.