I have browsed through Shiva page a few times but I didn't see any Mac support. Even though I am interested in Windows only atm, I would like to work with Mac ports as well, I don't really care much about Linux though. Is there a proper Mac support for Shiva?
But Unity3d is also very impressive. The editor is the best of all indie tools. And the workflow is great as well. You can change a texture or model in external apps and when you switch to Unity it just reloads the assets. Perfect. Shaders are just a dropbox away in your material panel, just like in Shiva or C4.
Gamestudio is somewhat similar, you have to rely more on scripting, tools are a bit older. But you should compare yourself if Unity goes public on Windows.
So far I have only been working with trial betas of 3ds, I was about to get the commercial edition but then I saw (today actually) that Unity 2.5 will be out around the end of Feb, so I have decided to wait and compare both. Like you said, I am more into scripting than messing around with C++ (the reason why I didn't progress much with C4 :P) so a big plus on Unity's side atm is how instead of a custom script I will get to learn a useful scripting language (since I design Flash sites, I can really use some extra learning :D).
So, keeping watch on the news for release..
