I had a single cabin for the night before flying out in the morning.

What was good:

Clean and comfortable - the cabin was clean and the bed was ok

Good location -right in Terminal 4 -you can't complain

Quiet in the cabin -good soundproofing helps

Easy check-in and check out - very quick check-in and check out

What was bad:

Not maintained well - both cabins I had were a little tatty with the air-con nob having fallen off in one and frayed edges in various places. That said, it was a stop-off so I wasn't overly worried.

Poor plumbing - At 12:30 in the morning the drains started to make a gurgling noise. Within 5 minutes my room stank like a toilet. I stumbled out of bed -half awake and went to reception

Let down by customer service - I wasn't overly happy with the drains but was knackered so didn't bother complaining but went to reception and explained. I was offered another room key. I then asked for help with my bags as I really didn't fancy carrying all my suitcases down the alley. I was informed that this wasn't possible but that I could take my time.

The concept isn't good and I suspect I was just unlucky but for me it was a really rubbish stay,

This hotel room is great for overnight lay between connection flights. It is very compact but enough for rest. It is very clean and bed is comfortable and electrically positional. The shower rain head is great! They rooms should be noise proof. You can hear the automatic corridor door all night and the steps of people on the hallway, which is an elevated wood floor. They give you a set of earplugs which is handy but, it has no use, because if you actually wear them, you won't be able to hear the alarm to wake up to get ready to check out and caught the flight. It is a good alternative hotel room if you at least have 6 hours of waiting time between connections.
They offer free tram between the terminals. It will take at least 30 mins each way to get to the hotel and out to your terminal. It will be more convenient if this is located on the international terminal. Our flight arrival was late at night and ALL the restaurants were close. They only have coffee, tea and few drink options.

We booked into Yotel only because we wanted to experience something out of the ordinary and we were flying out of Heathrow the next morning, so it was convenient.
We were very impressed with the layout and engineering of such a tiny space. We had all the room we needed and were perfectly comfortable with enough storage for our luggage under the bed/sofa and a very functional bathroom.
The were two issues that prevented us from giving this an excellent rating:
1- We were constantly being woken up during the night due to our room's proximity to the check-in desk. Even though the hallway has HUGE writing on it reminding people to please be quiet, that particular room was absolutely awful for sleep quality. After all the engineering and thought that went into creating such a unique space, the owners would be well advised to invest in sound proofing those rooms. Not since the days of travelling "ultra budget" have we experienced such poor quality sleep in any hotel we've stayed in. Too bad.
2 - More seriously - several times during the night our room filled with the odour of jet fumes/fuel. Someone needs to look at where the air intake is located because we both got headaches from this.

Arrived very early in the morning after 20 hrs travelling and not able to book into hotel until the afternoon would have meant hanging around the airport for 10 hours. Checked on the internet and found YOTEL. Hotels near the airport were much more expensive and would have meant another bus or taxi to get to. YOTEL was as it stated. Small but very well planned cabin accommodation. I was traveling with my sister in-law and it was a great place to relax, freshen up and catch our breath before moving onto London city. Staff were very friendly and helpful and best of all there is a great little pub/restaurant right out the front and convenience store and taxi ramp just below. Great location, easy to find, great value, glad I checked this place.