I did
D23 Expo in 2017 as part of a combo Expo/Disneyland trip, and I honestly wish I'd just planned two separate trips. The Expo was amazing (though everything PP wrote about managing expectations applies), but I was so exhausted from it each day -- the waking up super early, the standing in lines, the walking from the hotel to the convention center and back -- that my plans to dip into the parks each night quickly fell apart, and I even ended up cutting my two post-Expo park days short.
That said, I wouldn't trade my 2017 Expo experience for anything. Getting to see all the living Disney princesses on stage at the same time was incredible (and had that been the only thing I got to see at the Expo, I would've been perfectly content). It's hard to say whether I'd trade an entire year of park visits for one Expo trip, especially this year. Now, the 2021 (WDW's 50th anniversary) or 2023 (TWDC's 100th) Expos might be a different story.