RUM is definitely a big value prop. I like keeping an eye on how quickly our site loads in different countries and on various devices.
For analytics we use Clicky and it's decent. There's a 3rd party Chrome extension which is useful for seeing, at a glance, how many people are on our site.
Another big value prop is integrations with services like Slack.
I am not a rails developer but I have seen that rails developer have alot of inertia and they won't switch to grails. Grails is only attracting Java developers who are fed up of exhaustive configurations. Unfortunately books written for grails also assume that you are switching from one of java to grails.
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