I've had Minky Starshine for two weeks now, have incorporated it in multiple projects and now feel comfortable saying that it is probably the best introduction to additive synthesis you'll find for the price.
The UI does come off as archaic and even baffling perhaps at first, with no knobs labeled. Upon mouse-over though things begin to make sense and a quick look at the online manual -- recommended whether you know additive synthesis or now -- will quickly uncover much of the mystery. This approach to UI design does make for a cleaner, probably smaller overall footprint on your screen and does become intuitive after the first few hours. There is an option to have labels displayed immediately beneath the controls if you can't be arsed to look at the top of the UI, which when activated displays the specific value and name of each control as you mouse-over it.
As far as presets go, this is not a preset-user's paradise... the 32 presets that are included show just the basic capacity of this synth. Full disclosure: i first came to this page in hopes that someone had released another preset pack! But for $29 i don't expect the 1000's of presets you get with higher priced synths.
The sound quality of Minky Starshine was the true dealmaker for me. Although it has no modular capacity, the routing of the 4 lfos and the 3 selectable envelopes-per-partial are rather sophisticated and lend themselves to great experimentation. You can conjure all sorts of strange PWM, fm-like metallic whirring and swelling pulses to show up with just a basic understanding of how the envelopes and LFOs interact. The Filter is infinitely variable between LP, BP and HP, and this too can be modulated by an LFO. Even without a true modular matrix, the options that are hard wired make sense and give rise to some unique results. There is a basic modulation effect that can give your tones a chorusing, as well as delays and flanges (which all come from the basic circuitry template). I find myself using this only to create a spreading of the basic tone, which can feel a bit mono otherwise.
For those unfamiliar with Additive Synthesis, or get baffled by other additives that offer 512+ partials and a slew of jargon to sift through, Minky Starshine is for you. My only warning though is that like all additive synths, you should still expect to learn for an hour or two to grasp how additive synthesis and PWM work together. It won't hurt though, i promise.
Wishlist for future updates: Tempo-sync'd LFOs, 2 additive oscillators (or more!), higher/selectable number of partials to work with (up to at least 64 would be nice). Panning controls/LFO's.