As far as I have understood, the main issue with using BURP for rendering a scene in Sintel is the fact that the scenes require massive amounts of memory.

We’re also testing 64bit builds of the clients, which might just imply (in the future) that we could move onwards from the current 1,5GB scene memory requirement limit that we must enforce. Unfortunately I think that our efforts on making the service more accessible and stable will not be on time for the final renders of Durian/Sintel. Perhaps for the next open movie project though?

- Julius Tuomisto / Renderfarm.fi

An Approximate Global Illumination System for Computer Generated Films
http://www.tabellion.org/et/paper/index.html

Abstract:

Lighting models used in the production of computer generated feature animation have to be flexible, easy to control, and efficient to compute. Global illumination techniques do not lend themselves easily to flexibility, ease of use, or speed, and have remained out of reach thus far for the vast majority of images generated in this context. This paper describes the implementation and integration of indirect illumination within a feature animation production renderer. For efficiency reasons, we choose to partially solve the rendering equation. We explain how this compromise allows us to speed-up final gathering calculations and reduce noise. We describe an efficient ray tracing strategy and its integration with a micro-polygon based scan line renderer supporting displacement mapping and programmable shaders. We combine a modified irradiance gradient caching technique with an approximate lighting model that enhances caching coherence and provides good scalability to render complex scenes into high-resolution images suitable for film. We describe the tools that are made available to the artists to control indirect lighting in final renders. We show that our approach provides an efficient solution, easy to art direct, that allows animators to enhance considerably the quality of images generated for a large category of production work.

I came across this paper.. Maybe it would be useful.

Temporally Coherent Irradiance Caching for High Quality Animation Rendering
http://www.mpi-inf.mpg.de/resources/anim/EG05/

Definitely, it should be a must have feature, it was really great!
We could avoid things like this:

http://d.imagehost.org/0223/gi.png

What do you think Brecht?

Continue doing your thing man, and don’t forget to enjoy it

I felt I needed to bump this thread and I hope that it is still read.
@ Brecht:
I know you’ve said that you’ve explored many different papers and solutions already, so I apologize in advance when I point you to this thread:
http://blenderartists.org/forum/showthread.php?t=93304
I’ll be posting in Blender artist too just in case this one goes unnoticed.