Well, as advertised on the imvu.com creator landing page, you can use any 3d editing software of your choice, they specify : 3ds MAX, MAYA, Blender and Sketchup...but you can use absolutely anything as long as you are able to export a FBX file at the end.
Now the real issue might be, for new people that will need tutorials for creating into imvu standards, mesh naming, materials and what not, that those will be scarce in different softwares on inexistent.
Everyone's best choice is indeed to use someting supported by the imvu creator community as you will inadvertentedly run into issues and you want to be able to find resources and people that can help with that in the community.
PS: What seems to be the issue with Blender ? you really made me curious about "hating it" , most people are just better accustomed to something else..but never heard of anyone strainght on hating it.