Consulting, lectures, books, artwork, meetups, coaching — any topic is welcome. Just make sure you’re writing about something you actually did yourself. Something you heard secondhand isn’t a review.
You don’t have to focus only on the good parts. Mentioning what fell short too helps other readers figure out if it’s a good fit for them.
If money changed hands, please say so. If you got it for free or received something in exchange, mention that as well. Reviews that don’t hide anything are the ones people can actually trust.