It's a very noticeable difference between AC on and off at part throttle in a 2.0L WRX. I turn mine off momentarily when getting ready to start from lights and stop signs because it bogs the motor down so much that it's hard to start smoothly. And trying to get the revs up off idle for hill starting with the A/C on takes a ton more throttle than with the AC off.
It may switch off at full throttle, but it's definitely like dragging around a boat anchor in normal driving with small throttle openings.