I'm concentrating on the sauna/spa as I haven't stayed in the adjoining guesthouse, although I have inspected the rooms, which are nicely decorated and appointed. However, the accommodation is on the expensive side, by Pattaya standards and, if you don't have transport, the location is not ideal, being down a long soi (lane) from the main road, about half-way between South Pattaya and Jomtien.
As to the sauna, for those who know the Bangkok venue, think mini-Babylon! There is a small outdoor swimming pool in a pleasant garden setting, a mini-gym, the usual selection of dry saunas and steam rooms, and cabins/cruising areas upstairs. Massage facilities are available. There is a pleasant restaurant offering a wide range of international and Thai dishes but, over a number of visits, I have found the food quality to be variable: the Thai food is better than the European. The wine, both red and white, is abominable, and best avoided.
Unfortunately, the sauna does not open until mid-afternoon and doesn't really get going until the early evening. Staff are a little laid back, and seem to change regularly. I suspect their rates of pay are low, even by Thai standards!
Sansuk is a pleasant, relaxing change from the beach scene, but beware the numerous money-boys who ply their trade on Jomtien beach in the afternoons and who make their way to Sansuk later in the day in search of new victims! Although the sauna officially has a strict "no money transactions" policy, many of these sex-workers are well known to the management and, as regular customers, appear to be tacitly tolerated if not encouraged.