In areas with a lot of lamps (2,000+ in a viewdistance=6 area), FPS goes to 10 fps (or less).
Upon loading new chunks with more lamps, computer stalls for a few seconds (0 fps) while it loads. Upon removing all lamps from the build, 120+ FPS was normal, with no stalling during chunk loads.

I assume this is due to the halo rendering affect of the lamps, could a config option be added to ProjectRed that disables the halo rendering function and any other fancy effects?

All of these tests were run on a very capable computer with a 4th-Gen i7 and an Nvidia GTX 770.
The lamp-intensive build

Considering the same thing would've happened if RP2 lamps were used, I'm not sure of what can be done. Too many of anything would cause lag. Making it a config option would be a possible solution, I guess.

@MrTJP this build has been around since mc 1.1 using redpower lamps and microblocks, I converted from 1.4.7 with redpower to 1.6.4 with the help of a tool that @Chicken-Bones made. I got roughly 80 fps under that setup. Point is, it's possible, a config option to make rendering a little less strenuous would be awesome!!

Are you sure it's the lamps that are the issue and not the microblocks?

Positive it's the lamps, i've removed them (replaced lamp ids with zero, leaving microblocks) and the FPS increased significantly! the microblocks don't appear to be the problem. As far as my profiling seems to show it appears to be something with the halo rendering.

Added temporary option to disable lamps via 38c923f.

Will remove said option once the rendering is optimized.