I have to say that sharkman had me chuckling quite nicely! Reminds me of a SciFi channel show about the same thing too, a genetically altered shark man!

If your characters don't require a >continuous mesh< (robots are a good example) or cartoon chars that have the separate body pieces hidden under clothing then MOI is good or great for those kinds of characters.

If you need a 1-piece or continuous mesh then while MOI will give you a decent (ngon) mesh, it may not be the cleanest mesh topology wise or perhaps too dense to work with for animation.

However there are other applications like TopoGun and Silo3D (even ZBrush 3) that will let you>retopologize< your MOI mesh(es) into a cleaner more animation friendly 1-piece mesh.

It's not less work, in fact it's more because you create your characters in MOI and then have to recreate them in Silo or TopoGun etc.

However as you mention, MOI is great for getting the designs in your mind OUT where as with other programs, your creativity is limited by trying to figure out how to push the polys around the way you'd like...

I've read a lot that says there's no right way or wrong way to do things in 3D; if your results are pleasing and they get the job done then it's RIGHT!

I say go for it! See how far you can take it...

-Will