After JB my iPhone 3GS with the new iOS4, I’ve been playing around with it and found some very neat improvement to the phone which most places don’t really mention it. First of all the OS speed and animation is now much smoother and faster like it’s been overclocked or some sort lol.
Lets now talk about some of the small small improvement which I find it’s really worth mentioning.
WALLPAPER

I know this doesn’t benefit JB users, but now you can set wallpaper for your home-screen.
MULTI-TASK

And the long awaited Muti-task function from Apple which is is good in a way but it doesn’t work for Cydia apps. And if you launch your games or apps from folders created using Categories and you activate the Multi-task to let’s say make a phone call.. you won’t be able to switch back to where you left off after that.
Another bad thing about the native Multi-task is, although it only runs partial of the app in the background in order to save on battery, but it actually eats up your phone memory. Luckily for JB users, you can end all the unwanted task using the SBSettings.
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CAMERA

One of my favourite update is now taking of photos on the new iOS4 is way faster compare to the previous version. They also added I think 16x digital zoom function as well as tap to focus for video recording.
MESSAGING

Another cool feature now is instead of auto suggest and change the word for you when you misspell a word. Now if the it detect more than one suggested word for the error, it will underline the word with red dotted line, so all you need to do is just tap on it and it will pop up with the word that you want.
CUSTOM WORDS

New from APPLE, you can now add custom words by going to Settings > Keyboard. Weird thing is you need to add either Chinese or Japanese keyboard in order to enable this function.
PHOTOS

Photos and video are now sort by type for easy searching which you can only see this when you enter the gallery via Camera. And they also added Geotag of photos/videos that you took from.
GPRS

Now there is a little Arrow symbol that tells you the GPS signal strength on your timebar when you launch any app that uses GPS
ITUNES

Some minor interface changes to the Itunes which looks pretty good as well.