Check out Kotlin though. It's seriously great and doesn't share lost of the performance penalties of Groovy
Particularly though, the static compilation is just not comprehensive enough. It tries to do type inference but it's limited and invariably you end up having to add type casts in ugly places to convince it that expressions are valid. Occasionally it actually flat out refuses to compile something valid and you have to find a different way to do it. Sometimes it compiles with one version of groovy and then is broken in the next. It works great though to selectively add to hotspots of code and in other places to speed them up and define them better.
Having said that, we are essentially using Groovy as a java replacement and for our team I think the above costs are well worth it. This is partly because we have a heterogenous application that is partly dynamic in its nature and Groovy's dynamic scripting ability is amazing for this. The fact we can code our whole back end in the same language makes it super easy and well integrated.
That's a bit of a myth these days. Groovy may even be more performant than Kotlin when used with static compilation.
Apache Groovy has inherited all of the syntax of Java. When Jeremy Rayner built the Antlr 2 based syntax for Groovy back in 2005, he began with the syntax for Java, then added the Groovy-specific grammar to it. The latest version of Groovy still uses that syntax, so if Java has syntactic baggage, then Groovy has it too.
I'm picking Groovy will still have that baggage-laden syntax for a while yet. 2 yrs ago, Daniel Sun built an Antlr 4 based replacement grammar, but the Groovy project managers at Apache are taking their sweet time in rolling it along. They even had its optional preview removed from the version 2.6 beta of Groovy.