I really like some of the sounds of HS (e-pianos, percussions, pads, accordions, nylon guitar). I dislike others (acoustic pianos without GP-2, brass sections, acoustic steel guitars, acoustic drums in the presets not clear enough because of the filter, I'll explain this later). Sound is always a question of personal taste, so it may be the best to listen to the demos on the Wizoo website.
HS has many many patches but just a few 'real' Combinations; that's a pity because they are really good. Most of the Combi sounds delivered are starter kits for multitimbrale arrangements, but not layered sounds. Some layers are included with the patches already; but I would really have liked to have more Combis. One big advantage: Wizoo released a free GM module (GM-4, ~100MB!) in Juli 2004. Great service.
The HS sounds are not fully editable; since version 1.1 it's at least possible to change samples to other ones of the same sound section. The filters are ok; what I personally dislike is the fact that active filters cut the hi edge of the sounds, even when CutOff is set fully open. Especially the preset acoustic drums sound a lot better if you turn off the filters (default: On).
Wizoo calls HS a 'workstation', and there really are some similarities to today's keyboard workstations (expandable, 16x multitimbrale, master and insert effects, many many patches), but there are also some issues that make it difficult to call this babe a 'workstation' (patches not fully editable, only few real combi sounds).
The performance is really great; on a today's computer (2 GHz and above) you can do a whole complicated arrangement without hitting the 50% CPU mark. Switching between patches is very fast compared to SampleTank for example.
The usability is great, too. The user interface is very straight forward, and six screen knobs called the 'hyperknobs' always control the most important parameters of the current patch, and can be controlled by external gear via MIDI CC - very useful.
I think the HS is a bit too hi-priced; the retail price is 399 Euro ATM, street price ~320 Euro. For 200 Euro, this one would be a real killer app.
I recently bought the GP-2 expansion module for Hypersonic (79 Euro), which gives you two new piano sounds: A natural piano using approx. 100 MB of your memory, and a really nice pop piano (70 MB). I like both sounds very much, found only two issues: The natural piano has one a bit 'darker' sample around C3 that's audible; that's a shame because the keys around C3 are some of the most used ones. The second issue: The hammer release noises on both piano models don't follow the stereo pan of the played key, which is a bit unrealistic (on the other hand: How many piano VSTi do you know supporting hammer release noises?). Apart from that: Good money to value for the GP-2.
Stability: Since GM-Module (1.1.1) some effects are not selectable anymore when editing; I hope this will be addressed soon.
The rating represents the plain HS without GP-2.