We stayed here for 3 free weekend nights in July (sorry for the delay).
As most have reported, the hotel is very upscale, with good service. The location is unbeatable. Central to everything in HEL.
We were given an "executive" room at check-in. It wasn't huge, but nicely sized, with a beautiful bathroom. As others have noted, the shower was amazing. Simply one of the best anywhere that I've ever experienced.
We noticed on the first night that the A/C wasn't satisfactorily cold. Someone checked on it for us and showed that it was blowing air... but not cold enough air. Oh well. On the second night, the inadequate A/C actually kept us awake. I called at 3am and said it was time for a new room. We were moved to one of the named suites (I don't recall the name) which was really something. As described by EWR ATC Hold, the living room had a library motif, and the bedroom was just off of this. The only quirk was that the bathroom ends up being a far ways from the bedroom due to a poor design. But we lived with that!
The sauna(s) was very nice. As described, Plats have free access. There are several to choose from, and we hopped about a bit. As it is co-ed, you need to wear your trunks in the sauna, though one or two of the men seemed to ignore this rule.
The staff was very friendly and helpful on all fronts. We did not partake of F&B at the hotel.