Great stay for Business Travelers &Vacationers
I've been staying at this hotel every week for about 2-3 nights the past 3 months for business. The main reason I choose this hotel is proximity to work, but also the price/value. This is a fairly large hotel. 
Location:
This place is in a great location. Mainly financial buildings, but not far from all of the clothes shopping stores. The subway is right below it and the E train will get you to and from Penn Station in 10 minutes. There are some nice restaurants near by, sushi, indian, etc.
Check-in:
Sometimes quick, sometimes slow. It's a hit or miss but they are pretty quick. They seem to check-in people every 5 minutes.
Rooms:
I've stayed in all of their rooms, Queen, King, King suite. Obviously the King Suite is their nicest and largest, but their Queen/King's have ample room. Bathrooms have mostly been clean. I did have one room with a slow draining tub and I could tell it could use a good scrubbing. The toilets/vanity have always been nice. I'm a very light sleeper and never yet had any issues with noise either outside or inside. The doors door slam sometimes and can be loud, so just be careful when closing your door. Speaking of closing your door, if you just let the door close, it won't close all the way! So make sure you shut it as you are either walking in or out. A/C is great, never had any problems. Make sure it's set on high, sometimes they are set a 1 bar, but that won't be enough to cool your room, make sure it's on 3 bars (changed via electronic control).
Internet:
As long as you are a Hilton Honors member, you could find a way to get free internet. I usually bring my own t-mobile hotspot and use it, as the hilton internet can be a little slow. But if you have nothing else, it gets the job done.
Breakfast:
If you get one of their breakfast rates, or have a high hilton honor status, you will probably get free continental breakfast. As you walk in, they will try to get you to upgrade $8 to their full breakfast, the hot items (sausage, eggs, bacon). I never found it worth it and if I ever ate down there, I just had coffee, cereal, some fruit. Not the best selection, but it got the job done.
TIP: I started going to the small shop next door. They make great omelets. I also grab their salads for dinner sometimes. The guys there are really nice and breakfast has never been more than $10. Coffee is great next door. The Coffee at the doubletree breakfast is always burnt.
Bar:
The Bar area is nice and the drinks are pretty good. WATCH OUT: They automatically put a good 18-20% tip on top of their drink orders. This means that bar tenders are not that friendly. If you order a drink, ask for pretzels/nuts, because they obviously won't voluntarily give you some. The Bar area has nice music and lounge seats. Much better than many hotels. Be prepared to pay a price for the drinks, Wine is an easy $10, other cocktails $10-13.
Gym:
The Gym is pretty nice and clean in this hotel and above average for most. There are about 4 treadmills, 3 ellipticals, 2 bikes. They have free weights from 10 - 50lb's and 4 machines for back/shoulders. They also have about 8 bicep bar bell weights ranging from 50 - 110 lb's. They have 2 stands for various exercises. The one annoyance is the ceiling is fairly low. I'm 5"10 and I can touch the ceiling with my hand. This means no kettle bell swings, or anything swinging higher than your head.
Overall I really enjoy staying here. Again, apart from sleeping and a little work, I don't spend time in my hotel. But the most important for are price, location, cleanliness, service, and gym. The doubletree has all of those.
I would give it 5 stars, but management needs to address:
1. Bar bill that automatically puts Tip, not cool.
2. Some bathrooms could get a makeover and the tubs/shower rubbed down