Unlike most granular synths, Grain Science was designed to behave like a normal synth. You've got all of the parameters you're used to, and it can be used as one of the best wavetable synths on any platform. Additionally there are many interesting assignable effects. The "science" comes in the form of elaborate modulation methods that go beyond typical ADSRs. If you want to get into the granular stuff you can sample, import and record your own sounds to tweak and retweak. There is full MIDI support (including Virtual), an excellent "MIDI Learn" implementation. Watch the full review here.
Development continues with a recent update that added an Animoog style ribbon controller, as well as an improved Arpeggiator and more effects.
Disclosure: I received my copy for review from Wooji Juice.