Yes, less rotating mass at the crank will free up some of that lost horepower, and direct it to the wheels. Well worth it.
However, be sure to get a lightweight flywheel, and not a "Lightened" flywheel. Lightened flywheels are stock ones that have been drilled out to lighten them, but it makes them weaker.
A new clutch would be good too, but I disagree that it should be required, there is less mass at the flywheel with this mod, so it's not like you'd need more clamping force to engage the gears, However, a better clutch would be a good upgrade to do since you have the tranny open anyways. get it all done at one time rather than opening it up multiple times, you know?