Doom has never been known for its multiplayer anyway, when I joined sam in august 2007, Doom 3 was already complete empty.
Sides, Privateer is right, the game is not balanced at all, the leveling makes you unlock stuff to take advantage on your opponent... which is retarded. Because people will join games, get destroyed by people who plays regularly, and will quit the game after being tired of getting owned.
Doom will be worth 19€ in my opinion, focus on solo mode.