We were there from Presidents' Day, 2/17, through 2/25 and experienced and saw everything that JimmyV did...we used CM ticket media and had to schedule "day of" Fp+.
We were surprised to see empty kiosks on Pres Day in Tomorrowland @ 9:00a.m. and we walked right up and a CM assisted us. The only difficult one was ETWB - the earliest Fp+ was for 11:55 p.m. so we subbed Buzz and also scheduled BTMRR and HM.
In DHS, we were able to change times without a problem. After we would use our first Fp+, we would go to an iPad CM and ask to switch our next Fp+ to "right now." This worked for RnR and GMR. Instead of waiting for 45 minutes for our next Fp+ window, we were able to go from ride to ride immediately. The CMs were very good in working with the scheduling to get the times we wanted and needed...we would go into a park a couple of hours before CM DD needed to be backstage and the CMs targeted that block of time for our Fp+ choices.
Because the system had been glitchy for Fantasmic Fp+, the iPad CM told me Fp+ wasn't available for the second Fantasmic so I Fp+ for the first show. When I went back for the second show, there were a few guests at the Fp+ tapstile. I then explained what I had been told and that I had wanted the 2nd show because DD performs in Fant and I needed to be seated in a specific area. They allowed me to enter and be seated in the Fp+ far left section of the amphitheater...at least three full sections of the amphitheater were completely empty for the second show. AND, the surprising thing was that standby guests were seated in the center Dining Package area while Fp+ were directed to the sections to the left of Dining for this second show (Diners get preferred seating for the first show only). It was interesting to watch this unfold!