rotrex makes several sizes. the C38 is used for S197s. it is capable of 600+rwhp here are some specs from their website:
the koenigsegg ccx uses two rotrex units to make 800+hp with a 4.7L engine! the efficiency rivals turbos, with up to 98% efficiency! Rotrex's website claims 98.4%.
http://www.rotrex.com/pdfs/Rotrex_Technical_Datasheet_C38_Range_V4.0.pdf
i am excited to see what it puts down. Forced Air Performance took an 08 Bullitt to SEMA and it put down 500+rwhp.
FAP said that after 10 dyno pulls, they could put their hand on the blower unit comfortably, it runs that cool. thats too much for me to trust the stock engine to handle. i know some have been lucky (like anthony) but i prefer to play it safe. I may have to install a different pulley to decrease the boost, depending on the numbers it lays down.