Is it worth the time to learn Mecanim for creating store assets with Unity basic?

From what little I have gleaned Unity basic does not have IK for Mecanim, which to me is already a pretty big deal when creating custom animations.

I am interested in uploading some rigged/animated characters to the Unity Asset Store, but all of my work has been done with the legacy system. I see in the reviews for several store assets that buyers are unhappy because characters are not set up for Mecanim.

I am assuming that if I create my animations in an external application (I am using Blender) that those animations are not transferable to Mecanim. Do I just need to provide an alternate character that has been rigged in Mecanim so that it can use other Mecanim animations?

I really don't want to waste time learning Mecanim if it will not provide any benefit to my assets.