It was bothering me that my gmail was not downloading automatically. So I went into settings/ mail, contacts and calendars. There I found that gmail cannot be set up to push - it has to be fetched. Mine was set to fetch manually, so it only loaded new messages when I opened the mail app. I set it to fetch every 15 mins and now I am waiting to see what happens. I thought this was worth posting as it is somewhat obscure in the guide.