watir better Implicit/Explicit waits than "stop loading"
Implicit waits
WebDriver lets you configure implicit waits, so that a call to #find_element will wait for a specified amount of time before raising a NoSuchElementError:
driver = Selenium::WebDriver.for :firefox
driver.manage.timeouts.implicit_wait = 3 # seconds
Explicit waits
Use the Wait class to explicitly wait for some condition:
wait = Selenium::WebDriver::Wait.new(:timeout => 3)
wait.until { driver.find_element(:id => "cheese").displayed? }