Just read at Mashable that Google is planning to add IMAP support to GMail and some accounts might have it already enabled. Well, I decided to give it a shot, and wow, the result was:

GMail gets IMAP integration meaning better features especially with email clients. Finally I can delete mails from client and read status get synced.
Update: In order to ensure Trashed, Sent, Drafts, and Junk mail messages are sorted properly between Apple Mail and Gmail’s webmail interface, a few more steps are needed: “How-to: Proper Gmail IMAP for iPhone & Apple Mail”. Basically you should “merge” Google Labels with corresponding Apple Mail folders:
Once your Gmail IMAP account is added to Mail, you’ll notice your [Gmail account] in the left sidebar.
1. Highlight “[Gmail] Sent Mail” in the sidebar and select “Mailbox” (menu bar) > “Use This Mailbox For” > “Sent”.
2. Highlight “[Gmail] Drafts” in the sidebar and select “Mailbox” (menu bar) > “Use This Mailbox For” > “Drafts”
3. Highlight “[Gmail] Trash” in the sidebar and select “Mailbox” (menu bar) > “Use This Mailbox For” > “Trash”
4. Highlight “[Gmail] Spam” in the sidebar and select “Mailbox” (menu bar) > “Use This Mailbox For” > “Junk”
However, deleting messages are not so straightforward as you would think: “What happens when I delete a message?“.
How come some Gmail accounts have the IMAP feature activated and others do not? I don’t see the option in my account, but I want it desperately.
Someone (MacRumors: Forum) found the following quote: “Sync your inbox across devices instantly and automatically. Whether you read or write your email on your phone or on your desktop, changes you make to Gmail will be seen from anywhere you access your inbox. Don’t fret if you don’t see “IMAP Access” yet under the Settings menu. We’re rolling it out to everyone over the next few days.” So it’s coming soon =)
How-to: Proper Gmail IMAP for iPhone & Apple Mail: http://5thirtyone.com/archives/862