Jailbreaking an iphone

[Oneeyedvic]

I have a 3GS iphone and am considering jailbreaking it (as there are a couple of apps that I want that are not available through the store - ie diary on front and tethering).

I have seen enough ways of doing it, but my question is:

Once I have jailbroken my phone, can I still use itunes or do I just use cydia and when I have finished jailbreaking the phone, does it restore (as I have paid for a lot of apps and don't want to lose them).

Apart from potential warranty issues, is there any downside to jailbreaking.

[Milvus]

Tethering is provided with the 3GS (except for AT&T in the USA) and there are plenty of Diary apps in the app store. Did you want something special in the diary?

[Oneeyedvic]

This is what I was thinking of for the diary: http://www.rockyourphone.com/index.php/intelliscreen.html?feat=y />
and tethering costs a fortune here - but you can tether on your 'normal' iphone allowance if you jailbreak.

Anyway, in answer to my own question (as have noe found out) everything works as before and I can still use the AppStore as normal.