I’ve been using the latest version of the iPhone software (iOS 4) for a few days now on my 3GS. The backgrounding feature is pretty cool, though I’ve only really seen it useful for listening to things like Pandora while doing something else on the phone.  I haven’t really found any other good use for it yet, though the quick switching between applications is cool.  I just wish that nearly all applications didn’t stay running all the time, making it optional would be nice.  Maybe there is an option that I just haven’t found yet.  I haven’t given it too much time.

Another thing that is great is being able to group apps into folders.  Before this I had maybe seven or eight pages of apps, which made it difficult to find what I wanted.  I did try to keep them all alphabetized, but now I have only two pages of apps.  The first page has a couple of folders but other than that it has my most commonly used applications.  The second page is all folders of various categories with the remaining apps fitting into one of them.  This really helps to keep things organized.  Of course all folders now have the apps inside them alphabetized for even quicker use.

Those are the biggest changes I’ve noticed so far.  I did download iBooks and a couple of free books.  I doubt I will ever buy a book as I prefer to get them from the library, but I’m hoping I can sync some library ebooks up to iBooks in the future.  I’ve noticed the threaded mailbox, but haven’t much time to use it.  The same is true with the 5x zoom that is now available on the camera, and places stored in the photos.  So far I’ve been impressed with the new features and look forward to getting more familiar with them.  Anyone considering the upgrade should absolutely do so if you are running the 3GS.  I’ve heard the upgrade can slow down the 3G, but I haven’t noticed anything like that on the 3GS.