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Before the huge changes to the store system the game was one of the best f2p mmos out there. The classes weren't super balanced but it was enjoyable, now free players apart from looking like peasants can't even afford a single weapon that isn't even a super/uber weapon unless they shell out some cash. There's a lot of new widgets that are there for the paying customers to give them a small boost.
If you're willing to drop a couple of bucks and buy yourself a weapon or two, and maybe a piece of clothing you'll enjoy it a lot. Otherwise you'll feel gimped and playing will be very frustrating.
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Like Kosto said, before the CS update, it was extremely balanced between the paid players and F2P players. Now that the update happened, it isn't the most balanced, but I'd say it's still better than most F2P FPS. I can still own CS players with non CS weapons. XD The ubers weapons are nice, but not required if you have skill.