So after nearly 3 weeks of sitting on a lounger I can give an update.
I can see why there could be mixed reports. We were on Sal and stayed in one of the RIU hotels. I couldn't fault the hotel and facilities available. The room was excellent, pool and pool area was clean with decent loungers; lovely sandy beach with lots of shelter; easy to get AI drink (inc coffee, soft and local alcoholic drinks). The local town was an easy 20 minute walk with a very nice paved path through the beach and some restaurants to a very scenic pier. The local vendors were friendly but nowhere near as pushy as those elsewhere.
The buffet food was some of the best we have ever had. A good choice (except for those that like to pile everything on their plate at every meal). On a couple of nights there was a mound of meat (beef, pork, turkey, veal etc.) and a chef cut off what you wanted and put it on the grill for you. I got a couple of fillet steaks, others were having sirloins that I would guess were 20-30oz. Cooked and seasoned beautifully.
The entertainment was a mixed bag. There was a neon night and a white night with a DJ blasting the dooph dooph music ... we had a fantastic time. There were a couple of circus type acts (very good) and local nights of music. The animation team was one of the best we have seen.
The downsides were that there were a lot of mosquitos and even our Jungle formula deet did not do a particularly good job (in fact it pretty much destroyed the effectiveness of the sun cream - see below). Beyond a one day island tour and walking into the nearby town there wasn't a lot else to do outside of the hotel. I believe Boa Vista (another of the Cape Verde islands) has even less.
I took ill for a couple of days ... I thought it had been something I had eaten. I went to the hotel doctor who checked me over and called a cab to take me to the clinic in the nearby town. The clinic put our NHS to shame. Lovely clean and very efficient. I had to wait for about 30 minutes then got called in for blood and a some other tests (less said the better); after a further 15 minutes the doctor called me in and gave me very detailed printed report of my results. it was not a food related issue ... thought to just have been sun stroke (so I stopped using DEET). The cost for all the tests was about £75. Lots of hydration and I was fine after a couple of days. The TUI rep was very helpful.
For guaranteed winter sun (mid to high 20's while we were there but getting hotter) it can't really be faulted and we are already looking to book again.