While a vast majority of iPhone users are enjoying the new features and performance improvement in the latest iOS, some iPhone 3G users have reported that iOS 4 has slowed down their iPhone, which has forced some of them to downgrade to iPhone OS 3.1.3.

It has also motivated someone to create a spoof Apple ad demonstrating iPhone 3G running iOS 4.

Comex, the iPhone hacking expert who has brought popular jailbreaking tools like Spirit found a post on ModMyI forums, which is recommending iPhone 3G users to disable Spotlight for iPhone to make it faster.

According to ModMyI forum user:

iPhone 3G apparently has trouble keeping up with indexing, ever since 3.x. Two days ago, I turned off Spotlight search (Settings-General-Home Button-Spotlight search-switch off all you don't use) because I rarely, if ever, used it.

Up to this day, my poor old 3G with iOS is way snappier than it was before, and I wouldn't hesitate to say it's as snappy as with 3.1.3.

You can checkout the video where he has compared an iPhone 3G running iOS 4 with an iPhone 3G running iOS 4:

To disable Spotlight for iPhone, follow these simple steps:

• Launch Settings app

• Go to General –> Spotlight Search

• Deselect indexing for all or as many items as possible

We haven’t tried it out but if you’re observing a performance issue on your iPhone 3G after upgrading to iOS 4 then there is no harm in trying this tip before you decide to downgrade to iPhone OS 3.1.3.

In case you haven’t seen the spoof ad then check it out below:

We wonder if similar improvements will be seen if Spotlight for iPhone is disable on iPhone 3GS and iPhone 4.

As always, let us know how it goes and if you’ve observed any improvements.