the only software that i find to be intuitive is software that i already know how to use.
as an usability expert i think that you have your work cut out for you and the future needs you.
i think that a particular hurdle that 3d software faces is that the creators are always short one dimension in terms of the interface. there is nothing intuitive about squeezing 3 dimensional data into a 2 dimensional interface.
solidworks, being a parametric modeller, is driven by constraints, hence requires a very specific methodology for form creation. this does lead to what i would consider a very slow, and unspontaneous form creation process… but soldiworks was never designed to save you time up front, it was designed to save you time in the development back-end… through the tedious methodology of defining every constraint of plane, curve, radii as you build you create a powerful set of relationships that can save you a tonne of time as you have to tweak parameters for manufacture and update drawings for ISO standards or whatever. but if you aren’t going to capitalize on those features then all that you are left with is a tedious way of building. the same is, of course, true of all parametric modelling software.
Surface modellers like alias studiotools and rhino can be much more fluid in terms of form creation… if you want to pull something, you pull it. if you want to move something up and over, you move it up and over etc. What you give up for this fluid process is the ability to tweak relationships after the fact. Studiotools does have build history which can be exploited but it is not, nor is it meant to be, in the same league as parametric modellers. Artistically, these packages can help you to create some amazing forms that would be extremely frustrating to creating in a parametric modeller.
But in both cases, parametric vs surfacing software, you have to work through a learning curve in order to understand the paradigm that they have use to cram 3 dimensions onto a 2 dimensional interface.
As far as learning where features are and how to move the model around in space… well… you kinda just have to learn it. i would say that the Alias Studiotools interface is a good one… but that is because i know how to use it. For that same reason i find Rhino’s interface frustrating… because i wonder why the tools aren’t where they are in Alias. I can also work quite fluidly in Solidworks, but that because i’ve been using it for about 6-7 years.
Sorry, doesn’t really answer the question. I suppose the answer to the question “what 3d software is intuitive?” is really “none, they all have a learning curve”. I would suggest that whatever package will give you the final results you require is the one that i would spend the time investment to learn… as usual, you have to know where you want to go before you can get excited about getting there.