Have travelled with them several times on packages and found them good. However their standards seemed to be slipping slightly in more recent years and we had cause for complaint (for which we got a partial refund) in relation to accommodation issues in Sicily a few years ago (in a place that we had visited several times previously with them and were well familiar with). Maybe it was a blip but it put me off them a bit. More recently we have used who we found better on the cost/value and customer service front.
I've found them pretty good, although they tend to be a bit more expensive than the likes of say Budget or Falcon if you're only going tothe Canaries etc. But the service is good and I'd have no complaints and would recommend them.
We used Sunway to go to Agadir, Morocco last winter on a package holiday.
If I recall correctly (and to my knowledge), Sunway was the only package holiday company operating from Dublin to Agadir, which was why we selected them.
Anyway, on this trip, Sunway was fine, and its local person in Agadir was superb!
One advantage of Sunway over others is or was that they always had their own reps on the ground - some others use third party reps who can be less reliable and helpful. Whatever about the problem we had as I mentioned above the reps did do their best to rectify matters. However part of the problem there was that Sunway had grossly misrepresented the accommodation on offer in their brochure and to us in person and this was the nub of our complaint and the basis for the compensation that we received.
Only complaint was changing of the flight times, originally booked to fly out lunch-time and fly back into Cork for 1pm. Flight times changed to late afternoon outbound and late evening inbound - which was a real pain - sitting round on the last day waiting to go home, got into Cork at 1am. The accomodation was exactly as offered and the rep was always about to offer advice or assistance.