EDIT: Also, cpu usage by cgminer seems to have greatly increased. I noticed these things with two machines running Windows 7.
I wanted to post the same observation. I've been upgrading every few releases and had been on 3.8-3.9 for a long time with a few BFL units. In 3.9 the CPU usually averages around 15%-16%. Going to 4.0.1 the CPU usage slowly increases and levels off at ~35%.
Ubuntu 12.04.4 x64, 3.11 kernel, gcc 4.6.3
CFLAGS="-O2 -Wall -march=native" ./configure --enable-bflsc