We were there 1/16 - 1/18 after cruise on the dream. Parks were busier than expected (not summer busy) likely due to MLK weekend approaching and tour groups.
We had booked our FP+ when first available and initially happy with the selections we were able to book. imo we failed 'the test'
With a 3 y.o. in tow we bailed on FP lines twice. The line for Star Tours was almost back to Indy. BTM's FP line wait was ridiculous. If you dig around here, somebody posted a picture of the FP+ that stretched back to the bridge by SpMt. We were looped thru posts & series of ropes to the right of the entrance but still a long wait.
What disturbed me more was the standby lines were really long, longer than I've seen them over past President's Day visits in MK. Kicker was the posted times were consistently far understated based upon length of lines I observed. I realize WDW often stacks up guests outside and there is a short end-run to the attraction boarding area but this wasn't the case.
I expressed concerns to CMs before we entered POC...guests lined out to walkway doesn't equal 30 minutes no matter how you stack them inside with both sides operating imo but was told the time had been newly posted. It took us a little over an hour to reach a boat. Same thing on Jungle Cruise. Standby listed as 30 minutes, checked with CM who verified the time...wound up escaping out the emergency entrance after an hour.
I'd book something ahead of time. we were able to switch existing FP+ times on iphone while in the parks as long as it is before the window starts. We didn't run into any technical bugs as to the system going down for our three day visit.
We have another short trip booked end of May. I hope that they've managed to get this current hot mess whipped into shape by then. Although, perhaps typical repeat guests will have decided it's not worth their time to visit and the decline in guests will afford shorter standby times.

The cynic in me is waiting for WDW to offer 'for fee' additional FP+ to guests.