My job is working as an artist in architectural visualisation - I was working for a company called Forbes Massie Studio until it recently closed, after which I joined a new team made up of ex-employees. We absolutely treat our images as a ‘photograph’ taken in 3D space. Once the ‘photograph’ has been captured in 3D and rendered we do a lot of 2D work in photoshop, ending up with something that is half way between a visualisation and a matte painting. Here are a couple of less architecturey examples:
I started out using Blender with the Cycles Engine back in university, however I now use 3DS Max with V-Ray. Blender is still amazingly powerful and there are plenty of brilliant tutorials on youtube.
My advise would be to not shy away from 2D post production. It can be easy to pour hours of work into crafting the 3D scene and perfecting materials, when often a simple texture overlay in photoshop ends up looking much better.
Really glad to see this subject come up on lines - interested to see who else is involved in the world of 3D!