sbt downsides:

    - slow resolution (could be really really really slow)
    - transitive dependencies could be a mess since it could actually will mostly give you a evicition but it's hard to actually resolve that.
    - however if you have two plugins a evicition is not printed, so you will actually get a funny stack trace if you actually use a library that resolve something via reflections. (i.e. closure compiler)
    - sbt is slow
    - sbt has some wierd operators.
    - has problem with dynamic ranged versions
    - scoped settings are cool, but could be wierd to understand, especially for new people
    - sbt-web which tries to use npm which it packages as webjars which actually is a total mess since you actually run into the great world of npm packaging and try to force it into a completly different format.

there are more, however these are the ones I often deal with