Liquify is really nice tool to make lots of adjustments in images. Earlier users didn’t prefer to apply it due to its destructive nature. The effect used to get merged in the layers itself when this filter was applied.
With updated version of Photoshop CS6.1 onwards, we can find new feature where we can apply Liquify filter to Smart Objects. That means even after applying this filter, we can reopen its dialog and carry on working from where we left off. With the help of it, we can now apply any tool further more or revert the image to its original state.
This has made Liquify more user friendly feature as we always have the opportunity to change our mind later after using it.