Well, I totally love Thea Render and it's my main Renderer for years.
- It's very affordable with great network rendering - an additional network node is 49.- Euro.
- It has GPU and CPU kernels, biased and unbiased.
- The GPU kernel ("Presto") is brilliant in that it also uses the CPU very efficiently at the same time as the GPU (optional of course), renders really fly and if one machine has not enough GPU memory, it simply renders on CPU only silently.
- Great material system.
- Falloff panels are very simple to create by mapping a gradient image on a quad-polygon-panel and use that as light. I use several HDRIs of studio equipment like umbrellas and spotlights that way.
- Good community, constant development, nice and clever developer, no update cost in several years with massive dot updates (the addition of GPU rendering was free!).
- It's very well integrated in Rhino (that where I use it the most these days) but also works just as well as a standalone ("Thea Studio").
- Comes with an ever-growing material library and other goodies.
- Bucket rendering for GPU - if you are low on GPU memory, use the buckets.
- Animate between different lighting situations.
- Many passes with deep EXR support.
....

Highly recommended.

Cheers,

Tom