Its main draw is the inclusion of almost everything you need for building most websites (templating, routing, database adapters, etc)
This is also its main drawback if you have strong opinions about which libraries you use. (Not that it's hard to switch out.) In this sense, it feels like a Rails "omakase" experience. Arguably, this is exactly what you want when you're diving into haskell frameworks.
Another big plus is the tooling and community around it. Everything is well documented (compared to other options) and even includes keter for deployment.
What do you dislike?
Disclaimer: I haven't used Yesod in about 1 year, so it may have changed quite a bit. Yesod uses Template Haskell and DSLs heavily which isn't necessarily a problem (when it works) but if you end up debugging generated code it gets a bit hairy. For example, I'd rather use blaze or something "purely" haskell than a DSL like the shakespearean family of templating.
Recommendations to others considering the product
It's a really great place to start. You'll find out quickly what you like and don't, and from there you can sub in alternatives that suit your needs. If nothing else, the documentation can lead you in the right directions
What business problems are you solving with the product? What benefits have you realized?
I've mainly used keter and persistent for decent sized projects in the form of microservice-type api's. The only cases of full yesod stack have been for minimal internal tools which were experiments towards deploying haskell stacks (which were quite successful with a heroku stack buildpack).
* We monitor all Yesod reviews to prevent fraudulent reviews and keep review quality high. We do not post reviews by company employees or direct competitors. Validated reviews require the user to submit a screenshot of the product containing their user ID, in order to verify a user is an actual user of the product.