I have to say a couple of things about TS. I taught myself TS2 in about a month. The interface is very intuitive and the focus of the program is excellent. I like having the one central view (I usually use it for perspective). I like the fact that objects in the workspace are discrete from one another. I also like having my layout tools integrated with my modelling tools.
My big problems with Truespace include those absolutely evil boolean functions, the subviews and the lack of layer support. The subviews are subwindows of the main window and cannot be dragged over to another monitor. This is a significant draw back, since those subwindows really eat up screen real estate. Also, layer support, while not critical given Truespace's handling of objects, would be ever so helpful. I know there are plugins that fake layers by selectively setting the 'invisible' flag on objects, but a true integrated layer system would be better.
On the other hand, it took me four months to learn Lightwave and I had to take a class for that. In the end, however, I find myself vastly preferring Lightwave for one simple reason: focus. Truespace focuses on a mesh. The mesh is all important. TS maintains a concept of an 'inside' and an 'outside' with a mesh and thus holes in the mesh are a problem. Further, poly-by-poly construction of a mesh is nearly impossible. Lightwave doesn't care about the 'solidity' of a mesh. It is polygon based, rather than mesh based. This difference in focus allows the creation a mesh bit by bit, rather than 'sculpting' as you do in Truespace.
Lightwave has drawbacks though: complete seperation between the modeller and the layout functions; the view system; and non-discrete objects. Shifting between Layout and Modellor just to get a test render is annoying and interrupts the workflow. Having your views as subframes of your work window makes it impossible to use a second monitor. Finally the objects are not discrete. Objects in a single layer are considered one object, thus anything you do (without explicitly selecting polygons/points/volumes) affects everything on the layer or layers that are currently selected.
If I could have Truespace with Lightwave's point/poly editting tools or Lightwave with Truespace's integration and mesh sculpting tools, I would be one seriously happy 3d geek. Oh, and if someone fixed those booleans: bliss!
I don't work with 3dsMax yet. I hear good--and bad--things about it.
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--Mik