I have too many synths. Correction: I have too many synths that are similar to each other and encourage me down a particular creative path. Sinmad is not one of those synths - I don't have anything else quite like it.
What I particularly like it for are percussion sounds and the physical modelling end of synthesis, although it can also do most of the things you would expect a synth to be able to do. The resonators and the feedback options are the most eye-catching elements of the design and this enables something else which I've not seen anywhere else, which is the capability to create guitar feedback in a semi-controlled way.
Also check out the randomise function which is particularly useful for creative serendipity. It's not simply a 'randomise everything at once' button - you can introduce levels of randomness to changes based on whereabouts on the panel you click. So you can almost tweak the settings with the randomise function, rather than throw out everything you've got, which means that you can feel your way towards a particular sound a bit more before you take control and adjust things yourself.
Full disclosure: I was given a free NFR licence of Sinmad for taking part in the 146th One Synth Challenge.