What does Zelle do well? Zelle is a straightforward payment service that works well for user-to-user transactions. Once it's set up, it's pretty easy to use and deposits directly into your bank account.
What does Zelle not do well? Zelle is not as easy to set up as other solutions, and it really doesn't stand out much in the fairly crowded payment service page. The main difficulty with setting up is that you're asked to select a bank, and if you're bank's not there, it can be a little intimidating for some users and they may not want to keep using it.
What do you wish you had known about Zelle before using? Zelle seems to be less-known, at least in my circles, than other big names like Venmo and Google Pay. Although you're able to add a card if your bank isn't listed, it's not really 100% clear how exactly they're making that work. Is there a fee? Etc.
Have you used a competitor to Zelle? If so, how does it compare? I've used the Cash app, Venmo, and Google Pay, and I prefer all of them over Zelle, in part because they're better-known (so more people use them), and in part because they're easier to set up and use.