The Hotel Gli Dei is situated on the top of a very steep hill, as previous reviews had mentioned, so that wasn't a surprise! The views are indeed amazing - Vesuvius from the back, Ischia and Pozzuoli at the front. Some reviewers had mentioned 'unhelpful' staff, but we found them really friendly, helpful and polite.
Yes, the pool is sometimes closed for functions, BUT this tends to be at around 1pm on certain days, and the hotel have obviously paid attention to previous criticism because they told us up front which days this would apply to - and it was 4 days out of our 10 day stay. On those four days we lounged happily at the pool in the morning, then did trips out in the afternoon, so it was really no big deal. Incidently the pool was bigger than the photos suggest, and there were very few people there apart from us; in fact, on one day, we had the whole area to ourselves!
For the amazing pool and the superb views there was only one disadvantage; the hotel is quite a way from the centre of Pozzuoli (a bustling, busy Italian resort with loads of shops, bars and restaurants). As we didn't hire a car, we did spend a lot on taxis. However, we wouldn't have wanted to drive, as the traffic in town was extremely busy at weekends - so that's up to you. If I went again I would probably hire a car for longer journeys - Naples, Vesuvius etc. We did our trips by train, which was easy and cheap, but return taxis from station were difficult to find, hotel will order them for you though.