iOs & iOs Apps (inc iPhone, iPad, iPod, iBrick)

I want to jail break an iphone 3G/3Gs to retain my vodafone contract.
The only reason for getting one is because I've heard you can do FULL 2 way sync with google calendar (i.e. I put an entry on my phone and it appears on online and vice versa).

Your experiencies?

I have a feeling you will lose a significant amount of functionality if you jailbreak but stay on o2. Have a google but I think you might lose voice mail, iTunes and I have s feeling you might even lose your free unlimited Internet. Without which the iPhone is just a mediocre phone.

I may or may not be talking out of my arse though...