“Anybody have a favorite for charting on the client-side?”
Google charts works well for getting something simple going quickly, use Flot for anything beyond that. Some people mentioned the existence of Raphael.js, but nobody had much experience with it.
“We had to make sure we were using rvm as a function instead of a binary and-”
You installed it wrong – the install checks that rvm is a function.
“We are seeing a lot of errors (more than the hoptoad limits) going to hoptoad and newrelic for error types that are handled by rails built-in rescues, like 404s for ActiveRecord::RecordNotFound. The app is serving up the correct error page, but still sending an error to the services.”
These services hook in lower than that so they can get all error info. Make sure nothing happened to their config of which errors to ignore, because they have their own way of skipping them.
Also consider turning off the default route to cut back on crawlers. This would likely just trade 405s for 404s, though.