As a veteran player with over 1,000 hours on Warframe, I HIGHLY reccomend this game. You get to see the past of the first Tenno and warframe; how awesome is that?! I haven't beaten the game yet so I can't say much lore-wise, but I feel like warframe players would love it just because you get to see how the warframes and tenno came to be. Essentially, this is where the story all began, and I think its cool seeing how it evolved.
After beating the story-mode/maingame/whatever u wanna call it, I think it was cool. Maybe because I played Warframe before playing Dark Sector made me think highly of it, but who knows; maybe I'm actually a flying ninja squirrel with the power to make ice-cream-filled gummy bears fall from the sky and cause chaos by attacking civillians with their base-ball cannons. Essentially what I'm trying to say is, I loved the game, but even for those who may not like it for who knows what reason,(aftr reading a few other reviews seems like some didn't think too highly of the storyline,) you may enjoy it if you're a Warframe player just because you get to see origins of the frames and you can also see how the game of Dark Sector evolved into Warframe.