I have over 2000 hours in it, in that time I've spent $100 on ingame currency. I an honestly say it's one of the best games I've every played, or technically 6 of the best games I've every played because Digital Extremes has this habit of making a whole new game and just building it into Warframe. They've got skateboards, spaceflight, mech fights, small game hunting, fishing, horse races, and street fighter. You can decorate your house and your giant clan hall, you can customize your gear for peek fashion, you can customize the little spaceship you fly in loading screens.

Easily the best thing in the game is that the paid for currency is tradeable. You can trade valuable in-game assets to oust players in an open market for it, effectively meaning that if you can't or don't want to spend money, you can still get the cool cosmetics through grind. Moreso, while you can buy most things with money, the only things you need the money for is cosmetics, everything else is pretty easy to earn in-game and it isn't until you get to the late-game content that it becomes a little grindy.

Lastly, it's co-op. You don't play against other players, so you never run into those feel bad moments where some whale or an ancient like me cleans house, instead we're more likely to pick up new players and Sherpa you through later content to get frames or gear. The community is just super nice.