Recently completed a three night stay at HV Plaza in a King Plaza Executive room. Upgrade as HH Diamond from King Plaza room (so not really an upgrade, as we would have received EL benefits as Diamond anyway).
Very nice hotel visually, if modern-Deco is your thing. Rooms are spacious and bed very comfortable.
Breakfast in the main restaurant (Emile) is quite good, with pancakes, waffles, omelettes etc made to order (although they don't actively promote this) along with buffet. EL breakfast is fairly standard, but quieter, if the bustle of the restaurant gets to you. Did not sample afternoon tea in EL, but evening drinks were quite good, with 2 - 3 hot dishes (usually pasta and another item such as sliced roast beef), along with the usual cheese and sandwiches. Wines were local and of a good quality. The evening spread could pass for a light supper if that is your wont.
We ate one night at Emile and the food was quite good, good value and the service was attentive.
Location is great, with tram stop on the doorstep and only a short stroll into the historical centre of Vienna and some very good restaurants nearby.
My only negative comments would be in regard to housekeeping and service, although the service issue seems not uncommon in Austria, so I wouldn't consider it particular to HVP.
A good, to very good hotel, at the right price or on points (or company expense account!), but not one you'd be happy to pay rack rate for, given the lack of attention to detail / service misses.
V.