With the nearly palpable anticipation and excitement surrounding yesterday’s iPhone 4 launch, many have been eager to get their hands on Apple’s latest piece of hardware as well as its software, iOS4.

Though the new mobile OS has been available to 3G and 3Gs owners since Monday afternoon, for many, today marks the first hands-on experience with the 100+ new features iOS4 brings with it.

While features such as multi-tasking, a unified mail inbox, folders, and enhanced camera features were highlighted directly by Apple, many of the other enhancements were not mentioned at all.

Some more subtle than others, there are numerous “hidden features” of iOS4. While these changes are small, they work in conjunction with the other larger new aspects of the OS to deliver a vastly improved and streamlined user experience.

iPod

Apple has significantly improved the iPod component of iOS4. The most striking update is perhaps the ability to create custom playlists right from the device. As opposed of the limited “On the go” functionality found in previous versions of the software, iOS4 users can give their playlists unique titles and create as many as they’d like.

The album view has also been retouched. When selected, albums feature an enlarged artwork tile as well as some basic metadata. This data includes: the year the album was released, the number of songs, and the runtime.

Spotlight

The built-in search feature of iOS4 has been tweaked to include web results and a direct link to Wikipedia at the bottom of each search. This convenient feature makes searching a snap, and has the potential to replace dedicated search specific apps.

Notes

Apple has finally enabled notes to join the ranks of mail, contacts, and calendars with syncing to MobileMe. This feature can be enabled by visiting Settings > Mail, Contacts, Calendars > MobileMe.

Calendar

iOS4 finally allows for calendars to be turned on and off. For users with a lot of calendars this will likely come as good news. Previously, only a selected calendar or all calendars simultaneously could be viewed. Now you can pick and choose to help keep things uncluttered.

Mail

With the unified inbox garnering most of the attention, it is easy to overlook several of Mail’s other new features. Message threading is a big deal. If you get a ton of emails daily, threading can help keep you organized within a certain conversation. Mail has also been upgraded to take advantage of custom email service features. For instance, custom alias are now offered in MobileMe, and archiving has been enabled in Gmail. Apple has also allowed for attachments to be sent to 3rd party apps (a feature first introduced on the iPad).

With new features big and small, iOS4 is as revolutionary as the new iPhone 4. A free upgrade for any user with a compatible device, the new OS is the biggest evolution of the mobile platform since the introduction of the App Store in iOS2.

This is just a taste of the many refinements introduced in iOS4. If you have any more that you’ve discovered or would like to share, email me!

See Kali’s iOS4 article for instructions on how to upgrade if you haven’t already!