You can never predict what another player will do. It's much more exciting experience. It CAN be bad as well at time - but it's not as bad as many other online games.
And don't let anyone tell you that Open is terrifying and full of gankers and griefers who are only looking to destroy your ship for teh lulz. Yeah, they're there, but they usually hang around the most popular and hottest systems - Community Goals, new discoveries, Engineers etc. Then you have instancing and time zones coming into that as well, so it's nowhere as bad, as some people would like you to think.
And even if you come across some unsporty players, you can always block them, which will ensure you won't matchmake with them again in the game (unless you have the same people on your friends list, as that takes priority when matchmaking).
I would wholeheartedly recommend it. I play pretty much exclusively in Open and I've gazzilion times more positive and interesting experiences there than the bad ones.
+1 from me - GO OPEN!