Do you recommend any particular alternative to New Relic? In particular, I'd be interested in something that helps answer the questions "How much memory am I using, and what's using it?" New Relic helps a lot with the latter question, as it can aggregate request time by Rails action. E.g. it can say "30% of your Apache workers' time is spent in this one Rails action." Which helps you understand what's driving the need for more Apache workers, and thus the need for more memory.
We have pretty cool technology to correlate events into bigger buckets (problems).It is based on tracking of each individual transaction flow through the stack plus discovery of infrastructure topology and performance.
