I'm experiencing a hight CPU usage (over 100% - reaching sometimes 125%) every time during a transfert is running.
I'm running Cyberduck v4.6.5 on a Macbook Pro 13" 2012 with 16 Gb RAM under OS X Yosemite 10.10.3.
The screenshot shows that total current CPU consumption by user processes (including Cyberduck) is around 26%. From the ps documentation.
%cpu The CPU utilization of the process; this is a decaying average over up to a minute of previous (real) time. Because the time base over which this is computed varies (some processes may be very young), it is possible for the sum of all %cpu fields to exceed 100%.