What can’t you do with the iPhone?

The third version of the iPhone’s operating system, demonstrated today by several Apple executives, accelerates its evolution into the Swiss Army knife of mobile computing.

Apple Senior Vice President for iPhone Software Scott Forstall, who led the presentation along with Apple vice president of iPod and iPhone marketing Greg Joswiak, said this “major update” to the iPhone software includes 100 new features.

The addition of perhaps the two most requested features, MMS (multimedia messaging service, which allows audio and photo files to be sent via text message) and cut and paste should quiet some of the harshest criticism of the iPhone.

Since just about every competing smartphone already offers those two features, they were way overdue in the iPhone.

Nevertheless, the cut and paste feature looks particularly well implemented and easy to use. My favorite part: shaking the iPhone serves as the “undo.”

Apple also said it has solved issues with its push technology, which allows the iPhone to “listen” for such things as e-mail and instant messages, sending them automatically to the iPhone without the user having to do anything.

Push was promised for the current version of the iPhone software, but developer requests for extended capabilities delayed it until now (at least that’s the reason Forstall gave).

Beyond those major enhancements, the new iPhone software includes many other welcome changes.

For example, users can search not only their contacts, but also their calendar, iPod music, e-mail and notes. Just as on the Mac, the feature is called Spotlight and is available from a new, additional Home screen.

Many users also will like the ability to use the landscape keyboard – which makes the individual keys wider and easier for fat fingers to hit accurately – in all of Apple’s apps, such as Mail and Notes, not just the Safari browser.

Several of the iPhone 3.0 features pitched as tools for developers – Apple is giving developers more than 1,000 new APIs – could result in a variety of clever new apps for users.

Peer-to-Peer connectivity, either wirelessly via Bluetooth or via the dock connector, has tons of potential. It allows the iPhone to recognize and connect to other iPhones or devices by using the Bonjour automatic network discovery protocol built into Mac OS X.

As an iPod Touch owner I wonder whether this feature will be enabled on Touches upgraded to the 3.0 version of the iPhone OS. The Touch does not have Bluetooth switched on, but when iFixit disassembled a second generation Touch last fall it found a chip capable of both Bluetooth and FM reception. (Crossing fingers.)

Also intriguing is the new ability to control hardware accessories. Forstall demonstrated how the iPhone’s equalizer, for example, could control external speakers.

Something developers will appreciate is how Apple has made it easier for customers to make purchases from within apps. Now people who buy a magazine app can buy a subscription right in the app. Likewise, a game app can offer additional levels. Of course, developers need to add this support to existing apps.

Thankfully, the “In-App Purchase” feature will work only in paid apps, not the free ones, so “you won’t be asked to buy something in that app,” promised Forstall. I think this is a good idea, but I hope developers won’t abuse it.

The changes to the iPhone software show Apple plans to keep pushing the platform forward aggressively. It will remain the envy of rival phone vendors, all of which are desperately trying to copy it.

Some statistics Joswiak gave at the start of the presentation illustrate just how big of a phenomenon the App Store has become. The number of apps has exploded to 25,000 in just eight months, with the total number of downloads exceeding 800 million. That won’t be easy for competitors to duplicate.

Developers can get a beta version of the iPhone 3.0 OS as of today so they can start building cool new apps; customers will get it “this summer” (no date was given). The update will be free for iPhone owners and a $9.95 upgrade for iPod Touch customers.

All previous models of iPhones and Touches can run the new OS, but not every new feature will work. For example, MMS won’t work on first-generation iPhones because of a slight difference in the hardware.