I'm playing a Deep Stalker Ranger in an OotA game. Currently we are 7th level.
My thoughts:
Immunity to difficult terrain is really, really powerful. We've changed it to immunity to naturally-occurring difficult terrain. The ranger can move normally across swamps and ice and rockfalls, but gets slowed by hunger of hadar.
The awareness one is pretty much unworkable, placing a massive demand on the GM. Hey, I use primeval awareness in the centre of Neverwinter. On the other hand, in the convoluted spaghetti map of the Underdark, knowing that there are humanoids 400 yards away doesn't really help much.
Darkvision is an interesting social feature in the Underdark. Wait, you're a human, how the heck are you seeing in the dark??? In a party of half-elves, my human character stands out. If you play one of these, get goggles of night. Darvision 150ft FTW!
The front-loaded combat utilities are great when you get the drop on the enemy (three attacks at advantage with hunter's mark damage, oh yeah!). When you don't get the drop, not so much. It is an interesting contrast between the paladin, who gets to choose when to nova, and the ranger, whose nova is determined by initiative dice.