I had all 3 of mine there, last one almost a year ago. 1st was a bit of a nightmare (v long labour followed by emergency section), they left me alone for far too long and yes they sent my OH home for that very reason - although my contractions were every 2 to 3 mins I wasn't yet 3 cms, so supposedly not in established labour. It was an utterly awful experience and the after care was v patchy and grumpy.
Next two births (elective cs) were much much better, both in terms of the birth experience and after care - they seemed to have improved things hugely since my first. 2nd time DH wasn't there at all (long story) and they were just so so kind and understanding and brilliant, the midwives were just amazing. Most important thing is do not be afraid to ask for things and speak up if you have questions, do not let them send your DH away (why on earth did I let that happen first time????) They can be v busy and leave you and so you have to be fairly strong on asking for stuff and prime your DH to be strong and clear about what you want too. Daytime staff were always amazing. Night staff often a bit more grumpy and unhelpful.
C&W is a fantastic hospital. I just spent a little over a week in there with DD as she was v v ill and it reminded me how amazing they are and just how many fantastic doctors are there on hand when you need them (I have never seen so many consultants in one room - not to mention all the teams of registrars, students etc etc). If you are an interesting case in any way then suddenly you are swamped with more doctors than you can possibly imagine so be prepared as it's a teaching hospital(that's what happened with my first birth - hours on my own, then suddenly more doctors than you could shake a stick at - remember you can tell the extraneous ones i.e students etc, to go away).
I have private medical insurance and yet when I suddenly needed a major operation, it was NHS C&W that sorted me out - I was admitted within a couple of hours after problem discovered and when DD became so ill recently I was straight into NHS C&W (for future reference remember they have a dedicated paediatric A&E). In neither case did I have time to sort anything out privately and they were there for us and utterly utterly amazing. You can be sure that you and the baby are in safe hands there.