NoCtiS_NoX on 22 November 2009
I am guessing that the premium service is like the gold on XBL. You can still play online for free but I am guessing that you'll get more on the premium service (that you'll have to pay) that you can't have for free.
Maybe:
No lag, more dedicated servers for both 1st/2nd and 3rd party games.
You'll get demo for games very early.
You'll get discount on PSN games and DLC
More services like QORE and etc.
