First impression:
The attraction is underwhelming. If the objective is to inform the uninitiated about Walt's life and achievements, the film does a decent enough job, but curiously forgoes spelling out milestones such as "first cartoon with synchronized sound" or "first feature-length animated film" in favor of insipid, unenlightening repetitions that "Walt never gave up." Okay.
The AA doesn't really look like Walt. The face is bloated and cartoon-like. This alone calls into question the attraction's raison d'être. The AA is probably impressive, but its shortcomings in appearance and audio distract from any groundbreaking qualities it may have. The general public's mileage may vary.
Beyond the AA itself, the Walt AA scene as a whole feels like a missed opportunity. There is almost no transition from the film to the scene; the curtain simply raises and Walt appears (contrast this with Lincoln's dramatic introduction in Great Moments). The scene itself is pretty brief. The set is smaller than I expected and not particularly impressive or interesting. The dialogue chosen for Walt is not exactly the most profound thing he ever said (will guests appreciate Walt's sentiments about his mailman brother or find it condescending?). And then the scene just kind of ends.
The lobby exhibit is delightful and will introduce casual guests to the idea of concept art, audio-animatronics, and the evolution of Disneyland. The exit hallway mural is a gaudy downgrade.
In light of Walt's alleged instruction to Blaine Gibson regarding building an AA in his likeness, this attraction doesn't exactly justify violating the founder's wishes. I don't particularly care for it but I hope other guests enjoy the attraction and find it informative.