neither response is accurate. you DO need to use pop if you're adding your pop account to your gmail account. once you add a pop account (you can add up to 5), it IS pushed to your phone through your gmail account. and you cannot specify a fetch interval for these imported pop addresses, they are determined by google. last night it was fetching pop emails like every 2 minutes. today it's outrageously slow, every 50 minutes or so.
the pushed pop emails appear in your gmail inbox, and you can label them anything you like to separate them (most usually just use the email address as the label)
you can specify that any replys to your pushed pop mail gets sent from either your gmail account or your pop smtp server.
you can also specify a signature to use for your pushed pop emails. overall the service is pretty slick, the only downfall as of now is that you're at the mercy of google for when they decide to fetch your email from the servers and push it to your gmail box.