No one workstation is going to meet everyone's needs - nor was I expecting Hypersonic to do so. I own other synth-sampler plugins. I primarily wanted a "scratchpad" with which I could have immediate access to my creativity. In this regard, Hypersonic is more than satisfying. I can always go back and substitute sounds from other VSTis later.
User Interface: very intuitive and easy to learn. sounds are categorized by type, they load quickly, and it's easy to set the mix for each patch. Many commonly-tweaked parameters such as attack/release can be adjusted on the fly via "dials" on the bottom of the display. And any changes that you make to a sound are saved when you save the host sequence file.
Drums: there are some good drum sounds, and the way the kits are programmed makes it easy to set pan, effects, etc. for each sound group (kicks/snares/etc.) The "Drum Kit Constuctor" is the coolest and most intuitive method I've seen for customizing your own drum set: you can use the wheels to dial in the sound you want for each drum on the fly.
Synth sounds: a lot of good synth pads and bells. Not a loser in the group. Huge selection.
Pianos: the grand piano is very usable and works well within a mix. The sound may be a little bright for classical, but it works well for pop....definitely a cut above the pianos found in the average hardware workstation. The electric pianos, however, I was not as impressed with; they lack dynamism.
Strings: the ensemble strings have a realistic "body" - but the ensemble sound is a little too small and thin for my taste (I prefer rich, lush string pads). In addition, the abrupt attacks and releases sound Mellotron-ish (this problem can be mitigated somewhat by editing the envelopes). But within a mix, these strings work well.
Unfortunately there are no solo or section strings.
I wasn't too impressed with the harp....sounds more like a new-age "synth harp" than a real concert harp.
Woodwinds: unfortunately this was disappointing. The flute seems to have too much of an octave overtone, and if you strike a note hard it does an octave pitch leap (which is not always what you would desire). In addition, there is no oboe or english horn; the double-reeds are represented only by a fuzzy-sounding bassoon.
The alto sax is excellent - but the bari sax sounds like the alto sample tuned an octave lower....not cool. Where's the buzzy edge, the bottom-end kick?
Percussion: some good sounds here (particularly the ethnic percussion), but the "tubular bells" aren't realistic at all.
(In all fairness, most "workstation" keyboards don't have great orchestral sounds either. Since I have GPO and SR's "Symphony Strings" on order, the lack of good orchestral sounds in Hypersonic doesn't bother me).
Bottom line: a good all-around workstation for expanding your palette and sketching out your ideas. For $300 you can't go wrong. Have a look at it before buying SampleTank.