I think likes offer a way to express a reaction to a note. They are definitely useful. It will be interesting how the ediquiete around zapping, liking, boosting/quoting develops. Lots of lingering habits from old ways of sharing information.
Discussion
I "like and not zap" posts about Bitcoin and Nostr, if I like the post. I do the same for content that I like, but is not an original creation of the author.
For the rest of the posts with original content, or if it really just makes my day, I will give my minimum zap amount, if not more.
Is the post valuable or not? If so, then zap. That is the true meaning behind "value for value", since other icons/reactions are subjectively just an emotional payment.