I am a new RO 90 owner also - so new that on the way out of the store I picked up a flier advertising the 10% off sale. I didn't return it, but I did come back and buy some boxes of 80, 120, 150, and 220 Granat.
My introduction to using it was taking down the residual wood on a 22" by 50" slab of maple that I had flattened with my OF 1400 and a rudimentary MFT/3-based router sled. I used some of the sample sheets that came with the RO 90 set and then went back for more when the sale started. As this was my first Festool sander, I'm still on the learning curve for using it, but so far I am really happy with the results. For a large surface, the RO 90 takes longer. On the other hand, I'm not under any time pressure and I enjoyed the extra practice time. 80-grit on ridges in the aggressive mode was quite a workout, while 150 (where I am so far) on the flats is a delight. No dust in sight, either, and I'm working in my living room.
The next bit of work my RO 90 is going to do will be on the table's legs. They are going to be in ash, 2 pieces of 4/4 glued up with some saw/router/file/RO 90 shaping.
