What do you like best?
The DSL provided by SBT has been thought to be used by humans. It hugely contrasts with other build tools based on XML where readability is poor at the best.
The fact that the project definition is build using a DSL within Scala helps as the user improves his or her skills in this language.
Plugin integration and ecosystem are great too.
What do you dislike?
When using command line mode, not interactive, you need to group each command with its parameters within a single string. e.g: sbt clean "runMain org.apache.... ...MainClass".
Version upgrades usually break compatibility with plugins and, therefore, with some projects.
Recommendations to others considering the product
Learn Scala before trying to do complex builds with SBT. Start playing with toy projects and, when you feel confortable with that, you'll be able to use advanced features as shading.
What business problems are you solving with the product? What benefits have you realized?
Project build and dependency management as well as artefacts deployment and docker image generation with the assemblyPlugin.
I also use its great integration with Scala's REPL in interactive mode.