SP lacks but MP is fun and balanced like chess.
The ranking system lacks once you reach the highest possible military rank and evolve into numeral rank, but until then each game is a contest to accumulate the most points, which makes for very intense battles.
Ranking up your military rank will keep you addicted for days, maybe weeks (depending on your skill), and will make you use teamwork. But once you reach the highest military rank you will begin to only worry about your kill/death ratio. This is just one reason why most players use the recon (sniper) class. Another reason is the special toys that the sniper receives. While each class has his own toy(s), only the sniper gets binoculars to laser-guide a missile from the sky which can be manually controlled by the sniper once called in. Oh, and he also is awarded the only motion sensor.
Even though the sniper is definitely a favorite, the game is somehow fair and balanced, and will entertain you for dozens, maybe hundreds of hours.
(Probably a rental, but also a worthy purchase)