Slick is not without flaws. After using it for more than 2 years and following each new release, I ran against its limitations quite often and started looking for other DB libraries that supported some kind of type safety.
But of all the other libraries I tried (jOOQ, ScalikeJDBC, and some others) none of them were as elegant and easy to use as Slick, although some of them are easier to set up.
Right now, Slicks SQL queries are not optimized, so you better use a db that's good at query optimization (i.e. not MySQL 5.6, which will do unnecessary full table scans for some of slicks generated SQL)
Slick has indeed some flaws, and for some projects these might be crucial, such as the query optimisation or some parts of the documentation.
But it's a rather elegant solution for working with a database and I'm sure most of these issues will be solved over time. Imo certainly a library to keep following.
But of all the other libraries I tried (jOOQ, ScalikeJDBC, and some others) none of them were as elegant and easy to use as Slick, although some of them are easier to set up.
Right now, Slicks SQL queries are not optimized, so you better use a db that's good at query optimization (i.e. not MySQL 5.6, which will do unnecessary full table scans for some of slicks generated SQL)