Another issue not covered: file downloads. Let's say you have a process that creates a dynamic image, or logs in and downloads dynamic PDFs. Even Selenium can't handle this (the download dialog is an OS-level feature). At one point I was able to get Chrome to auto-download in Selenium, but had zero control over filename and where it was saving. I ended up using iMacros (the pay version) to drive this (using Windows instances: their Linux version is very immature comparably).
Mechanize doesn't really have a proper doc, but just about everything you'd need could be figured out from the very lengthy examples page on their site.
Playing with it now, and while it seems to hit my download need, I can't seem to get it to play nice with sites that are JavaScript dependent. Am I missing something, or is there a way to plugin an underlying WebKit engine?
PhantomJS is capable of downloading binary content from js dependent sites but it is a journey to get it working as it is not an out-of-the-box feature. Instead use CasperJS to drive Phantom and get a ton of snazzy features including simple binary downloads. Happy scraping!
