I used it. MrNC phoned at 8am to say I was in labour and my waters had gone, and they said both birth pools were available if I wanted to come in, but if I was comfortable, I might as well stay put.
Went in a couple hours later - I found it lovely. Huge room, en suite bathroom, wonderful 2-tier huge beanbag that I knelt on for the next two hours, snorting gas+air. Then used the pool for 6 hours, with more g+a. Went through two midwives' shifts, both of them were great, checked in on us every 15 min or so, often staying and chatting. All amazingly laid back, and they agreed to give me two hours more than guidelines when nothing had happened, before I'd have to transfer downstairs.
My pelvis fell apart so I had to have an epidural to deal with that, and spend the next 18 hours on the delivery suite. Room was small for two people to stay with me overnight, but all the care I received up to birth and recovery was fantastic, getting explicit consent for everything, explaining why they might want to do X and what might happen if not, etc.
Sometimes the Carmen Suite shuts at night but the evening I was there they managed to get staff to stay open (Carmen herself, in fact!).
Postnatal care can be a bit ropey at night - just be prepared to ring your bell lots as it always gets answered quicky, but the person may not be at all useful. During the day (I was there 3 days) it was pretty good, with good bf support.