I currently have a iPhone 3G now at the end of contract so I  am looking into a new mobile soon and can not decided the best choice between WP7, Android and iphone 4.

if I could get any help on the pros and cons of each that would be very much apprised. 

Honestly, I don't see how all of those touch-based mobile OSes are dramatically different from each other. They all seem to be pretty similar experience for average user if wanting just "whistles and bells", at least in my opinion (and I am certainly not a geek but average Joe in this regard). The only visible aspect is that iPhone (and possibly WM7) appears to be more solid experience out of the box, yet I know for sure that lots of people actually love "pimping" their handsets. So even if Android is more "nerdy", it is not in clear disadvantage here.

 My point is: unless you are "power user" or corporate one, choose a device which you would just love to have, not OS.

well this is what i think thus far:

Win7:

- different interface then iphone and android.

- seems better catered for professional people that want to open doc files 

i really haven't played much with this so that is all i can comment

iphone4:

- pretty much the same as old iphone, so you know how that goes

- lots of cool apps

- less freedom

android:

- similar to iphone  in style.

- less apps

- more freedom to do things

- flash and html 5 support in next version of android

I think this point is getting more and more irrelevant. The best apps in mass segment (like games or lifestyle) will find their roads to each and every of OSes anyways. There is zero of exclusivity, unless we speak of corporate software or platform restrictions (which modern OSes produced in  bigger amount than older ones, amusingly)

Win7:

- different interface then iphone and android.
- not a lot of apps out right now
- all apps will work because of minimum hardware requirments
- one Marketplace
- free demo's which you can convert to full apps..
- xbox live
- no flash
- no multitasking
- no hot swapping sdcards (needs a factory reset)
- no porn

iphone4:

- games
- your old apps are compatible, just sync everything with it
- great discounts when apps are on sale
- less freedom
- 1 appstore
- lots of apps, difficult to find the right one.
- you could jailbreak it
- Apple tax
- no flash
- no porn

android:

- many models to choose from
- less apps, more crappy apps, more free apps
- more freedom to do things
- flash and html 5 support in next version of android
- Can't update your android version if your phone manufactur doesn't want to update it.. (I'm looking at you Sony Ericsson!)
- You could root it if you wanted the latest android version (freedom)
- fragmented appmarket, many publishers have their own android app download page, default android market has a lousy payment options
- fragmented hardware device may lead that apps aren't optimsed for your phone or not work at all..
- porn

No.. most games & apps are iPhone exclusive cause the average Android user doesn't actually buy apps..

in June 2010 google had paid out 21 million dollar against the 1 billion dollar Apple paid out to developers..
Android users are used to get free apps (or they can't pay cause of the lousy payment options google uses in the android market thus leading into different android store from developers themself which leads to fragmentation) while iPhone user are used to pay with the appstore.. and not all developers are willing to make optimized versions for the different phone models & android versions out there..

Actually I didn't argue about this fact. I just said that it's not so relevant and will be even less so. I will find Opera Mini , some nagivation soft, and some quick game (like Angry Birds or anything else similar) everywhere, and honestly I lack interest in exploring what's else there. And even if I won't find then there will be a substitute "good enough". If some useful app is released on iOS tomorrow, and will become a big success (to warrant my interest in trying it), it will be released then on other popular platforms.

Thanks for the Help guys.

As you in Australia, I don't know if different carriers effects things in the same way it does in America...

But I would I would chose Android. WP 7 definitely isnt there yet, missing basic things like copy and paste and any sort of multitasking. The iPhone has a wider selection of apps, but I would take a larger screen and more hardware buttons over that anyday

Depend on the apps you already buy/have, maybe better take the new iphone as you could transfer them to it (normally).