* Much more approachable config.
* Its clustering is easier to setup.
* Eventhough logstash is a bit heavy for my taste, the whole ELK stack is really nice for aggregating server logs.
As things are, one can always direct an app sever's syslog to a logging fleet running logstash (or elasticsearch running embedded logstash): http://cookbook.logstash.net/recipes/rsyslog-agent/
It looks pretty promising, but I have yet to meet anyone who uses it.
https://blog.mozilla.org/services/2013/04/30/introducing-hek...
That's what logstash-forwarder[1] (formerly lumberjack) is for. It's in Go, not Java.
[1] https://github.com/elasticsearch/logstash-forwarder