Emojis in passwords would both make passwords more secure and easier to remember for some people. The drawback is that they're very hard to enter in normal, physical keyboards.
But does it really improve security that much? If password is short, it's still gonna be quick to crack.
Only if the cracker is brute-forcing instead of using common passwords mixed with dictionary words, and if the brute-forcer thought to implement emojis. Given how many emojis there are, it would by psychotic to include them in a brute-force attack unless you already know the person used emojis.
Unless you pick the passphrase for them, you're not really gaining the advantage of the search space size.
PS. No I don't use it anymore. And yes xkcd 936 was my inspiration.