Really great value
Stayed in this hotel for five nights last April with my mom, on her first trip to the US. She's a smoker and there's very little in the way of affordable, well-located hotels nearer . On a punt, I picked the HI 6th Avenue. And it turned out to be a good choice. 
Rooms were really quiet and spaced out well. The nearest ice machine was close by too. The bathroom was spacier than I thought it would be. TV was big and there were lots of channels - (read all-day Judge Judy marathons) to distract us.
The hotel is well-located near Whole Foods on the 7th Avenue, so we grabbed salads or snacks there. The nearest subway is a couple of blocks away but it was okay. The nearest wine shop is a bit of trek, so plan to grab bubbly and what-not. Also, there's American Apparel Warehouse store nearby on 6th Ave for discount clothes shopping.
A couple of the goods and bads below, but a highlight for us was the last night when we decided to stay in and eat in the restaurant. Okay on first glance it looks like a conservatory in the 70's meets the Twilight Zone, but we had a good night. After ordering the chef came out with about our order and asked about it - how would we like it. A little chit-chat. It was great. Our meal was amazing. We decided we'd order a second beer, and the waitress told us we'd save if we'd order a pitcher. And we did. Lovely service to end our stay at the HI 6th Ave. Kinda symbolised our stay there. 
My mam is already itching to go back to NYC. She has her heart set on returning to the hotel. 
A couple of goods:
Rooms were of a decent-size - It was my first trip to NYC, and I have been reading nightmare reviews of teeny rooms sandwiched together. I was impressed with the size of our room. I booked through Hotels.com and was pleasantly surprised.
Staff - The staff were amazing. Checking in, managing luggage, hailing cabs and suggestions for places to go were managed with a friendly professional tone. I made a couple of calls and feared the phone bill, but it wasn't a problem. 
A couple of the do-betters: 
Slow lifts - The lift took ages to travel. We were one of the lower floors, so were weren't that badly inconvenienced. It's a busy hotel, with limited lift resources, so the naturally slow lifts were always under pressure aka busy.
View: While our rooms was of decent size, the view faced onto the back of building that worked as clothing factory. A tall building, at that. Smoking rooms take up a few of the lower-level stories, so you may need to suck it up. The view didn't really annoy us off much as were out and about every day, but a city skyline would have been nice.