Thank you so much for your feedback! 
1. its a tech demo, not much to see in it so hard to give a full feedback. i would have wished some more possibilities, like some blocks to place (even if they are pre-placed and i can just pick them up and rearrange)
Yes, unfortunately the demo is quite limited... I guess the upcoming building update will make it much more interesting (at least for people who enjoy building) 
2. i really like the sounds of the Java-version but somehow i expected to hear more new or remodeled sounds. thats probably my own expectation that failed me but i still think this game in new clothes deserves some new sounds as well 
Hmm... actually we did rework most of the sounds
In some areas we still use sounds which are similar to the Java version, but most sounds are new or at least improved
Is there a specific sound (or a specific type of sounds, like footsteps or hit sounds) you didn't like?
3. It seems i can´t destroy the wooden cabin im starting in. Though one or max 2 hits with the pickaxe are enough to destroy most objects in it. From my experience its very easy to accidentally click too fast / too much and bang - your precious object is gone. There should be some kind of prevention for that. Maybe it should need more hits to destroy an object.
Yes, construction elements aren't fully implemented yet so the cabin (and stuff like the fences) can't be removed right now 
4. on the other side i have hit the closed on the inside several times and got a quite cool and deep sound. not very fitting to the closet but i like the sound itself. however the closet didn´t get destroyed. but when i hit the doors just once, the whole closet collapsed. i made the same obersvation with the feeding crib outside the cabin.
The closet takes 8 hits until it breaks, it shouldn't really matter if you hit the doors or the body 
Do you really think the hit sound does not fit?
I'm not sure if sounds are played a bit different on our end... do you maybe have a 5.1 or 7.1 setup? Or is your device configured as 5.1/7.1 in Windows (sometimes this seems to happen even though a stereo output device is used)? I've seen cases where sounds don't work properly in these cases 
But please keep in mind that sounds are a bit different inside buildings^^
5. everything on max, even resolution and view distances i had some minor stutters. nothing to worry about. with massive terraforming it got a bit worse but still playable. though i can see it changing when there is more building going on. ill keep an eye on that 
Do you mind sharing some information about your hardware, especially your graphics card? 
9. i enlarged a wooden bench to something a fat-butt giant could sit on. LOVE IT!!
Hehe, yeah, the ability to resize objects certainly introduces a whole new set of possibilities 