I'm afraid I must agree -- I am suprised about the CPU usage of PicoLog (PLW32.exe V5.12.6 on WinXP Prof SP2).
PicoLog certainly does show up in the taskmanager as using all available CPU power as long as it is running. (Interestingly, it doesn't matter whether or not my ADC-11 USB is plugged in or not!)
However, it hasn't ever affected my other applications (e.g. causing delays,...). Hence, it seems to run with a lower priority (which it doesn't - it runs at the "normal" priority, check in the task manager). Nevertheless, the fan of my laptop is significantly more audible when PicoLog is running suggesting that the CPU isn't just doing NOPs.
Needsless to say that I am suprised (and a bit concerned) -- surely, if all other programs are able to only require CPU cycles when doing actual work this can be implemented in the PicoLog software.