I think this thread is a good starting point for me to come out of the shadows of a long (long looooong) time reader and write something (hopefully) valuable. 
Just a little background: I own Carrara since version 5.x and now what it can do and of course where it behaves more like toybox. I’m also a well trained user on a daily basis of Poser since version 4.x and I think I nearly know all glitches in version 6 (to the extend that I will never touch the integrated “FireFly” engine again). My first all over the top and beloved modeler is “Wings 3D”, with “modo 103” and “Hexagon 2.5” in the pocket for more complicated tasks. And I frequently use POVRay/MegaPOV to and extend that I can say I’m a POVRay script nerd. 
This was just for saying, I’m far from a professional 3D artist but an enthusiastic 3D fan. So I am in comparable position like you, truenovice. And as an so to say serious hobbyist my eyes fell onto “messiah” for nearly three years. I own the version 3 but I hadn’t had the time to get in swing with it (I know, I know, shame on me). But of course I had some playtime with messiah. Here are some thoughts, that hopefully get some light onto your questions:
2. messiah compares to DAZ/Carrara
Since I’m a Poser user I never felt the urge to install DAZ|3D and play with it. So no comparison to that. But from what I know from Carrara and the things I have seen in the included scene demonstration files that come with messiah and what I have seen in this forum I must say Carrara is simply no comparison to messiah. Messiah looks more like the heaven for animators. Which is not surprisingly because messiah starts it’s life as an Lightwave add-on for animation. The renderer came later. And the renderer in messiah is Carraras node based render system on steroids.
Cararra feels more like a software where the makers are satisfied by a huge feature list. But if you look closer many features are not well implemented at it’s best or are simply buggy or non functional at worst.
In contrast everything in messiah does really work. And it works well. It feels balanced and useful. Of course you must learn how to use messiah which is true for every application but after that there’s no hidden “nono” inside the application.
3. messiah import of models
As you know I come from “Poser” and I use “Wings 3D”. So my preferred import format is the .obj format. Unfortunately messiah is a bit picky by choosing a file. For example: Exporting a typical Poser-figure as an .obj from a Poser scene and importing that into messiah simply does not work. You have to import that into “Wings 3D” and simply export that again. After that messiah swallows the wingyfied .obj with no problem (Wings 3D does some re-arrangement of the “group” and “usemtl” statements inside the .obj which messiah likes and most other applications don’t care).
The size of an imported model does also matter. Poser figures are relative small compared to figures designed for 3DSMax or other applications. Taking Poser figures directly into messiah gives strange rendering artifacts (where I’m not sure if I missed a switch somewhere in messiah). By scaling the models with a factor of 100 which can be during Wings 3D im- and export the artifacts vanish.
4. messiah speed
Messiah rendering is fast! My god is messiah fast!
Ok, Poser is snail on tranquilizers, that’s for sure. And also POVRay/MegaPOV is not the fastest renderer on earth. By using Global Illumination which is done with Radiosity POVRay get’s even slower.
Carrara is an other chapter. But once you switch on Global Illumination inside Carrara, you again find yourself tapping your fingers on the table (or with lesser quality the picture looks bad).
Messiahs Global Illumination is simply fun! 
Conclusion
For me “messiah” was the chance to get the hands on a truly professional application and get the feel of it. Messiah is no toy, it’s a tool. It’s done for people who knows what they do and who want to earn money from what they do. Just from the feeling of what I have seen so far I never ever would try to complete a professional task with Poser or Carrara (hell, really not). But I would love to do one using messiah.
Or in other words: It’s the best toy for that money if you are willing to dive deep into the system and are willing to learn.
Regards,
The Inflater