I do architectural work. I love designing and modeling with MoI3d. I do use it in tandem with Rhino. Rhino currently has features that MoI does not ... dimensioning is a prime example. It is coming to MoI in the relatively near future. Rhino reads MoI files perfectly so switching to add dimensions and other features is easy. I do currently need both programs. I usually do as much as I can with MoI and then switch to Rhino for more finished work.
cheers,
eric