I learned TS5 wihout having even opened a 3d prog before, and without even reading manuals, I just clicked randomly the buttons the first days to understand the overall program philosophy, and as soon as I understood it, I found most of the buttons just were I supposed they should be.
Obviously it required more more time to understand the limits, the tricks and the best strategies, and I'm still learning, but It required (for many reasons) more time to understand the best way to creat ships for the game rather than to understand the best ways to use truespace.
I wasn't able to do the same with max (but admittedly I haven't spent enough time on it).
My opinion is that truespace IS easy and intuitive, and somehow elegant too, but it is organized in a different way than most of other progs.
From my limited experience and from what I heard from others, it is hard to switch from truespace to other progs, or from other progs to truespace.
Truespace is probably more suited for newbies: it has big limits compared to other packages, but (*almost*) all that is needed for lowploy models is there, and it has a pretty fast learning curve.
Once you get used to the on screen view control you don't even neeed other views except for very specific things, I work 90% of my time with only a window in perspective view saving a lot of workspace. I know you can do the same in other progs, but...it isn't the same:)
Probably the hardest step is to understand that most of the modelling tools are subdivided in object tools and point editing tools, that many tools will pop-up just by switching modality between object editing and point editing, althought almost all the other progs do the same (in different ways).
The only tricky part of the interface is to remember where the tools are, since the bars are compressed by default and many icons are hidden, and many advanced options can be accessed only with right click.
Believe it or not, Photoshop is organized in a very similar way, and probably this is why I found immediatly my way in truespace.
And don't forget that you can completely modify the interface: you can delete, move, add, copy icons, you can create custom toolbars, you can make em persistent, compressed, expanded, or pop-up bars, so if you don't like how the interface is organized (and if you know what the tools do), you can just create your own interface, completely different than the default one.
Since each 3d package has its own philosophy, it is very possible than some people will find extremely simple to understand a specific prog, and extremely difficult to understand others; but I'm talking about understanding how a program is organized, if you have problems instead understanding how/when use specific tools, how/when do things, well expect problems with any 3dprog