ICloud – Import/Send Gmail and Work Email to iCloud Online

Using iCloud doesn't really add new features for a Gmail user.

Contacts

Contacts on iOS are perfectly synced when using Google via Exchange.
Contacts on Mac OS X are synced using Address Book "Sync with Google" feature.

Calendar

Calendar is a bit more tricky.
On iOS, you have to activate each calendar individually in http://m.google.com/sync. But then, it syncs perfectly.
On Mac OS X, it can also be added to iCal, except it's via "Delegates".

It works but doesn't feel as just work as iCould does.

Mail

Mail has it's quirks, too.
On iOS, via Exchange, it doesn't bring all the Gmail goodness (archiving, etc.). And it miss push via the Gmail template.
On Mac OS X, via Mail, it's the same, archiving puts the mail in an "Archive" folder instead of the "All Mails" one.
Using an app like Sparrow resolve this issue.

To conclude, iCloud, like using the iWork suite instead of say Office, doesn't add value, but it feels more integrated with the OS (whether it's Mac OS or iOS).

You can setup your iCloud account to send using the Gmail SMTP server.

Setting => Mail, Contacts, Calendar => iCloud => Account => Advanced (Mail) => Outgoing mail server (SMTP) => Other SMTP Serveres => Add Server here you can set up the Gmail SMTP server: smtp.gmail.com - remember to choose the Gmail server, and de-activate the iCloud SMTP server afterwards.

The mails sent will however appear in iCloud's sent folder.

The iCloud sender email address will however still be the iCloud address. If you use the build in Mail.app, you can manually choose your Gmail address (and the mail will appear in Gmail's sent folder), but how you can use this one, the way you want to use it - I don't know.