I am surprised at the number of people who don’t know this, but it seems I run into people quite frequently who don’t know either that you can use google as an exchange account or that you can have multiple exchange accounts on your iDevice. There was a time when google only supported pop for gmail accounts. Now it supports both imap and exchange. The exchange service is limited to mobile device which means you can in fact use it with any of your idevices. Also as of iOS 4.0 you can have multiple exchange accounts on your iDevices which means you are no longer limited in that way.
Using google with exchange isn’t very different than imap but it does come with its benefits and downsides. Personally I opt to use exchange for my gmail account as the imap ports are blocked while on the network at my office, so this is a good way around it for me. Some of the other benefits you get is that you get the data pushed to you instead of your device having to fetch it. That means you get calendar, contact changes and emails as soon as they are sent. This also means less battery usage as your device doesn’t have to spend as much fetching. With exchange, you can also access all, or a limited subset of your gmail calendars and have their data pushed to you. You get all the benefits of exchange when it comes to scheduling appointments and inviting attendees. The main downside is the lack of the notes feature that you get with imap, allowing you to use the native notes app and store them with your gmail account. I am not sure why this is not available for exchange accounts in iOS.
To setup the account, simply go to settings -> mail, contacts, calendars -> add account. Make sure you choose Microsoft exchange as the account type. Then add it as you previously have, using your gmail address for the username. After hitting next it will attempt to verify and then ask you for more information, all you need to fill in is the server: m.google.com then you are all set! To setup calendars (picking and choosing which calendars you can access from each device) simple visit the following page from your device: https://m.google.com:443/sync/settings/ and login using your gmail credentials. You will then be able to choose which calendars to display for this device.