We are using SOLR in a production setup with a jRuby on Rails front end with about 20 different instances of SOLR running on heavy duty hardware. The setup is load balanced front end (jRoR) on a pair of machines and the SOLR backends on a different machine. We have plenty of memory and CPU and the machines are not particularly loaded (<5% CPUs). Loads are in the range of 12,000 to 16,000 searches a day so not a huge number. Our overall response (front end + SOLR) averages 0.5s to 0.7s with SOLR typicall taking about 100 - 300 ms.
How does this compare with your experience? Would you say the performance is good/bad/ugly?