Very impressive for a fan project. It faithfully recreates the entirety of Space Quest 3. No graphical issues or frame rate drops. Only the one issue I'd really call a bug. I haven't been able to beat Elmo yet so I can't speak for the dogfight currently.
I had a problem with both rock'em sock'em robots not responding on my second try. Other things that may have been issues: Astro Chicken was incredibly too easy; the terminator droid didn't give chase in the statue and came from the other side when I reached the pods so there was no chase or challenge to it; the garbage scow droid didn't see me no matter where I was, so there was no death there that I would have expected. I see the rat sequence was changed a bit so maybe that was intentional.
Besides those issues the game hit all the beats of the original. The Ortega sequence seemed a lot less janky than the original. The pole-vaulting was handled very well. I seem to remember the ordinance being more unstable and a greater danger though.
The only thing I really felt was lacking was the charm and polish of the original. I don't know if this is still in development, early access, or intentional design choice but it felt lacking in some of the animations, dialogue, and cutscenes. One other area would be the lack of the hand drawn backgrounds and characters, but obviously that had to change for the shift in graphical style/interface. 
Overall a great and successful project. I think if more polish and details were added with the developer's own artistic style and humor, this could really be a great remake that both long time fans of the series and new fans could both really enjoy alongside the original.