The alpha is quite good. Runs better then expected, even on high settings. Driving is fun, bit tricky. I had to make the car twice to get the hang of the building. I like the retextured block. The character is cool and the jet pack is awesome. Love the power connections, it's nicely done.
A few suggestions....
1. Vehicle speed could be fine tuned. Low speed, isn't really low speed, I'm still able to go over 70km/h
2. For creative mode building, a hover mode would be nice.
3. Being able to crouch to put blocks under blocks. With the editor you could get really near to the ground, in the game you cannot. If you build on a slight slope and work your way down (or even with oneven terrain) you end up with floating blocks. Also when you elevate your building and create a stair downwards, you cannot lay the last few blocks
4. The sun is too bright.
5. The day and night cycle is off. The darkness is too long, the day should be longer.
6. Will placing multiple blocks at once come back?
My first steps video shows the stairs and sun issues at the end