As with all forms of polymorphs, this is useful for a variety of purposes. The advantage of using a wand is that you do not need to be able to cast a high level spell, though there is a limited amount of charge in each wand. The most common uses include polypiling and trying to polymorph your pet into something high-level (but beware of system shock). Polymorphing hostile monsters is generally a last-ditch attempt, as it can create even more dangerous out-of-level monster types, but it may be useful in specific situations.
Also, if you have polymorph control or unchanging, and are surrounded by hordes of nasty monsters, breaking this wand can be fairly effective in getting out of the jam (whatever they become might be easier to deal with). You can also use this technique to polymorph hordes of pets into stronger ones, though be warned that you don't want to attempt this with pets that are too weak to survive the blast to begin with (such as jackals), as a mass pet die-off can leave you with very low alignment.
Beware, breaking this wand will polymorph you even if you are magic resistant.
Monsters can zap this wand at themselves, but mercifully, this will not generate out-of-depth monsters.
Wands comprise 4% of all randomly-generated items in the main dungeon, 6% in containers, 5% on the Rogue level, and 8% in Gehennom. There is a 4.5% chance that a randomly-generated wand will be a wand of polymorph.
Monsters can be generated with this wand as misc item if their difficulty is five or less.