1. You mean that the game takes to long to finish(that would be peoples own fault for playing to larger maps than they like to finish), or the game mechanics are simple to slow to be fun(like it takes to long to build things and stuff and there is too little to do in this game)?
Is the phase of base building and unit production at the level of Homeworld or slower? As far as I have understood this is a 4X-RTS game, and 4X games are not meant to be finished in 30-60 min, unless you are playing a very small map.
Schod was exaggerating. A lot.
2. Are the first 10 min always the same in this game?
In some ways the first few minutes are the same, in some ways not. Scouting, for example, lets you know the map around you -- and adjusting to that (on a random map, especially) can produce significant changes. There is
nothing like playing a random map and finding out all the planets around you require civic research before you can go anywhere with colonizing them!
3. How is the mood/music/style in this game, any good (how much % Jar-Jar and how much % Homeworld)?
The music is award winning. Hollywood could learn from this music

4. I have also noticed that planets in this game are connected with some kind of lines. Are these the only angles in which you are able to approach and attack/conquer a planet, or can you freely travel anywhere between the planets?
Phase lines control the routes you can take between planets -- it helps avoid issues where gameplay becomes "wack-a-mole".
5. And what about that battle UI previewed in Gamespy, can you use it's icons to tell your units to attack enemy units just by clicking on the icons (like, left click 1 friendly unit, and right-click an enemy unit to order an attack -/- open a order menu)?
You can right-click on an enemy unit to give a manual attack order, if thats what your asking...
6. Btw, im just wathcing a fanmade gameplay video right now, and it seems to me that there are these grey gravity things around planets, are these really the limitation of how far ships can go away from the planets, and how far away an attacking player can rally up his forces?

You cant move outside this rings?
Pretty much -- its called a "grav well". Inside one ring, your stuck with STL transit. Outside that, but inside the next ring, your ships are free to fire up their FTL drives
if they're near enough a grav well to travel down it. Generally ships aren't supposed to go outside that outer ring, if they do its a bug.
Apparantely, it looks like the small radius around planets in which your ships are allowed to move doesnt give much to tactical options, is this true? :.(
No. There is plenty of tactics. Not as much tactics as in some games perhaps, but the fact that you have actual strategy makes up for that.
8. Done watching (link: https://forums.sinsofasolarempire.com/?forumid=402&aid=148534#1).
One last question, are the explosions for bigger ships nice looking? It somehow seems like the ships just disappear before the explosion can get the time to cover the ships, and like if there is no parts flying around from the exploding ships.
The devs haven't released the final graphics to us -- IIRC, explosions are one of the things they just plastered something in for.