- code completion is not great compared to Java. For example one does not seem to be able to see the constructor parameters, or the method parameters can not be automatically populated.
- the plugin makes Eclipse *very* slow. Everything seems at least 3-5x slower. On the fly compilation is also much much slower than Java's.
Google Go focuses on the right problem: concurrency. It also is not constrained to JVM limitation (on the other side one can not use a Java library - but open source stuff is usually not too difficult to port from one language to another). It has one of the fastest compilers. It makes interesting practical choices: no inheritance.