Shellac has many advantages as a finish. It is non-toxic, dries quickly (provided that it is fresh), can be colored and is relatively easy to apply. There are also disadvantages, primarily that it scratches easily and isn't the most water-resistant of finishes. When shellac finishes get wet, they develop unsightly white rings.
Fortunately, shellac finishes are easy to repair. Shellac is basically a mixture of shellac flakes and alcohol, and applying additional coats of shellac to a previously shellac-finished project will cause the existing shellac to dissolve somewhat, allowing scratches and other imperfections to be repaired by simply adding a new coat.
Water damage is a different story. The damaged shellac finish needs to be dissolved with denatured alcohol. The denatured alcohol dries quickly, allowing new coats of fresh shellac to be added. If the previous finish was colored shellac, a bit of trial and error may be necessary with the new finish to match the color properly.
Cleaning up shellac on your brushes and tools is also a simple procedure. Shellac dissolved in alkaline solutions; it cleans up very easily in ammonia.