I am a beginner at rendering and have been using Flamingo nXt for over a year in the beta version and recently purchased the final version.
Flamingo is relatively easy to learn/use and is great for showing a customer what a part(s) will look like. I have mostly used it to render cast metal parts and it is great at depicting metal.
I think metal, plastic and generic color substances are Flamingo's strong suit.
I have tried rendering wood parts but find that it is difficult to get wood parts to look right and need to learn more about how to orient grain direction.
I reccomend Flamingo nXt but suggest trying it before you buy it to see if it suits your needs.
McNeel is an outstanding company in terms of their products and support.