My experience to date is limited to one wall and some popcorn(y) ceiling.
The Planex is a pretty phenomenal machine when dialed in.
I started this wall in our house and it took a couple of minutes to figure out what grit paper to use and how to set the speed of the head and suction. After a short time, it was easy.
The objective here was to remove the texture that is a sort of a "drag" effect.
I had previously only played with it a few square feet of wall and a little ceiling. I did the top and bottom of this wall in about 15 minutes. While watching me do it, my wife wanted in on the action and she did the middle part. It took her about a minute or two to get the hang of it. Incidentally, she's a 115 pound health care provider... For the middle part that she did, I took off the extension that comes with the unit.
I plan to remove this texture and the popcorn from my ceilings all throughout the house as part of an ongoing remodel. I know I could use other methods but this is easy and I like the result as opposed to skimming over or, in the case of the popcorn, using the wet and scrape method.
My experience with the abrasives is that the typical 120-180 or so Brilliant 2 might be good for new work. For taking down old chunky stuff like this, I'd look at 80 Brilliant or some Safir.
If you're doing the ceilings or a lot of high walls, the harness kit is a very good deal. You get the harness and the pole that parallels the Planex as a handle in a Maxi Systainer for $200. The Maxi alone costs more than half of that...
The CT 36 AC is a nice addition to the set as is the special hose and blast gate, which makes it work better on the back blasts. I did this wall with my CT 26 and had no problems but if I spent all day doing this stuff repeatedly, I'd optimize the situation.
That's my current observation. I'll have more to add to it soon... I was building sandpaper shelving when I took a break and noticed this thread.