Hi Rafal,
I've been using Logscape on servers running different Nixes ( Solaris, Redhat and Ubuntu Server). I have a few 2008 Windows servers in the mix. Getting installed was quite easy. I did have problems on Ubuntu Server because of OpenJDK so make sure you are using the jvm from Oracle.
As a Splunk alternative it appears to do everything we'd expect Splunk to do. Bear in mind that we are still at the evaluation stage and are thinking of adding more environments.
Rob