Hi Fed ...
I have been using MoI as my primary design tool for architectural projects for a few years now and after many, many years using CAD find it to be the best for my needs (residential and commercial projects up to a couple of million).
In my experience its only lack is easy dimensions and line types which I believe are 'coming soon'. Then I would also be able to use MoI for design through working drawings.
I suggest you buy MoI 3 now and start using the MoI 4 beta. It does seem to be bug free or nearly so.
cheers,
eric