As a user of Google Apps, I have found it a very disjointed experience up until now.

I now sync my mail, calendar and contacts to and from Google Apps straight to my phone. The mail is not push yet, but I am guessing they will upgrade this shortly (they just enabled this for Iphone and Windows Mobile).

This is very easy, you can use exactly the same method with Gmail as well.

1. Download the latest Nokia Sync software to back everything up. MAKE SURE YOU DO THIS, IT WILL SAVE YOU!!!
2. You need to download the Mail for Exchange onto your phone
3. Visit the Google Sync website for mobiles and follow the setup instructions
4. Spend the time organising your contacts and calendar, you only have to do this once.

Do you use Outlook on your desktop?

1. You can use Google calendar Sync to ensure that your Outlook has the same calendar as your Gmail calendar. I have used this while Outlook is still connected to Exchange and it works well.
2. Use an IMAP connection to sync your mail to Outlook.
3. The missing piece of the picture  - you can not easily sync contacts for free. I am guessing that they will release this soon.

Good luck