The Cave is real. 4 and a half hours on it today with two friends and a couple randoms and I got:
5 Legendary drops. Turned into a hand cannon, shotgun, machine gun, gauntlets and a cloak.
22 rare. a whole plethora of stuff, dismantled a lot of it but kept a good sniper rifle, and some other back up guns.
75ish greens. All dismantled. I have 245 weapon parts and about 200 wires.
Cryptarch is 1000 away from level 10.
I am shutting down the ps4 after a looooong 10 hour day of Destiny. I got more loot from the cave than I did the entire game up to this point, being a level 23. Going back first thing in the morning. Bungie is sure to patch this so I recommend getting in while you can.
Oh yea, a few of the blues were coins after decrypting so I bought exotic chest armor.
EDIT: Oh, and an event takes place every 30 minutes right at the cave so you get Vanguard, too. Plus, your Gilmore cards fill up FAST. Using consumables can also beef up glimmer from all the guys in the cave. I scored SO BIG today. Extremely excited.