Buy an iPhone 4S or upgrade my old iPhone to iOS5?

You’ve probably heard all the hype around the new iPhone 4S as it is Apple’s fastest selling device ever - pretty amazing given Apple’s track record of ‘magical’ product launches.

The iPhone 4S for the most part is an evolutionary device: it looks just like the iPhone 4 but as usual, Apple makes it faster, endows it with a better camera that can take some pretty amazing photos, and gives it some better battery life.

The real meat? The new Siri assistant and iOS5. First let’s look at Siri:

Pretty amazing stuff! And as an aside, I think Wolfram Alpha is about to get much more popular - it’s the engine behind Siri and can help you find out interesting things like what the weather was like:

or information about your city:

The downside? As it turns out, Siri is iPhone 4S only.

The silver lining

But for those of us with an earlier Apple device (iPhone 4/3GS, iPad/iPad 2 or iPod Touch), we can get in on the benefits too, just by upgrading to iOS 5, released today.

Check out the new stuff in IOS5:

Here are some great tips from our friends over at Tested.com:

How To Properly Upgrade to iOS 5 in Five Simple Steps

From improved notifications to iMessage goodness, here’s how to make your iOS 5 upgrade go smoothly the first time.

Our recommendation?

Have an iPhone 4? Just upgrade to iOS5.

Earlier device? iPhone 4S.

What are you going to do? Sound off in the comments below.