It's got all the important bits: Mario jumping, the castle, Princess Peach looking surprised. Along with the usual caveat that it's a fan-made, non-profit, please-Nintendo-don't-shut-us-down disclaimer.
Here's the latest development video showing the progress to date. You can keep up to date with the project over at its Facebook page, where the developers occasionally stream their ongoing work on Twitch.
[This Mario 64 HD fan project is coming along nicely - Destructoid]