For Net::HTTP, yes, checking the class of the response object is the way to do it. Using kind_of? (aliased also as is_a?) is a bit clearer (but functionally equivalent to using <):
response.kind_of? Net::HTTPSuccess
Calling value on response will also raise a Net::HTTPError if the status code was not a successful one (what a poorly named method…).
If you can, you may want to consider using a gem instead of Net::HTTP, as they often offer better APIs and performance. Typhoeus and HTTParty are two good ones, among others.