I find Carrara's metaball modeler (meatball modeler, LOL!) is another reason to celebrate the ongoing existence of Carrara.

Not all metaball implementations are equal. Many only have spheres, and they're not really that great to use. Carrara also has cube, cylinder, and a weird throw-pillow shape. You can also move, scale and rotate the individual shapes to refine your forms, as well as making forms that are positive and negative. You can set the degree of subdivision to get smoother forms, too. This seems very powerful.

The interface is a little stilted because the metaball modeler runs in its own room, but it's good once you get used to it.

I enjoy metaball modeling. The only one I recall being better was a 3DS Max plugin, but that was a long time ago. And I'm still getting comfortable here.