Hi Zymon,
I am an architectural designer and I use MoI to do all my modeling. I find it more intuitive than SketchUp. I will find MoI a lot more useful with Michael adds dimensions and linetypes. There are scripts that can be added for basic dimensions, though. I'm sure that built in dimensions will be added in ver 4.
MoI is very easy to learn but has a wealth of internal options so that even though I have used it for years I keep learning new things almost every day.
This is the best forum I have ever encountered with lots of experts willing to help with any question.
Try MoI for a week or two and you'll want to use it forever.
cheers,
eric