SBT has issues (I'd say performance primarily), but works really nice for what it does, IMO. Virtually no configuration required (for a simple project you only need to specify dependencies and maybe import IDE plugins), scriptable in a full JVM-based turing-complete language (Scala), sane per-project dependencies (packages are cached globally for the user, but whitelisted classpaths are dynamically generated for each project), and a consistent design (SBT plugins are really just library dependencies of the build itself, for example).