Thanks to Sony, I won't have the same doubts going into Killzone 3. Although the beta only allowed access to the game's multiplayer side, it's easy to see Killzone 3 is primed and ready to deliver.
Character classes were a major draw in Killzone 2 and return in the follow-up, only in a slightly altered form. All classes are available from the start, immediately opening up a good deal of strategy for newer players. It also gives players the option to play as the class they want rather than forcing them to work through other classes.