Apple only mentioned 10 of the promised 200 new features for iOS 5 during its Worldwide Developers Conference keynote. The first developer preview has been released to developers, and while specifics are covered under an NDA, new details have been leaking out like oil from an '87 Plymouth Horizon.

We decided to round up a few of our favorite leaked features we have seen so far.

Apple discussed its iMessage service, which allows sending text and multimedia messages directly from one iOS 5 device to another, including iPods and iPads. What Apple didn't demonstrate is the seamless integration with SMS/MMS messaging on the iPhone. When you choose a recipient to send a text, iOS 5 will check to see if that user also has an iPhone running iOS 5. If so, it switches automatically to use iMessage instead of SMS, and the interface switches subtly from green for SMS to blue for iMessages.

Besides ease of use, there's another side benefit to this seamless integration. If you send messages regularly to iOS 5 users, you may be able to switch to a cheaper texting plan from your carrier. Assuming you send messages exclusively to iOS 5 users, you may one day be able to ditch a texting plan altogether.

Deaf iPhone user Adam Betts noted that iOS 5 has new accessibility options for the hearing impaired. Users can set custom vibration patterns for contacts, similar to setting custom ringtones. Also, iOS 5 can be configured to use the LED flash on the iPhone 4 to light up when you receive calls, text messages, or other alerts. We're betting that some of you with perfect hearing will also appreciate these options.

iOS 5 will finally allow users to use FaceTime over a 3G connection. FaceTime has so far been restricted to working over WiFi connections, which limits its usefulness if both parties have to be either at home or connected to a reliable public WiFi network. According to 9to5 Mac, Apple will apparently leave it up to carriers to individually support FaceTime on their network, however. So while there's still hope for FaceTime, carriers may continue to handicap it with additional charges or outright bans.

Apple noted during the WWDC keynote that iOS devices are now first class computing citizens with "PC Free" features, including non-tethered activation, wireless iTunes syncing, and OTA software updates. To make sure that no PC of any kind is required to use an iPad, iPhone, or iPod touch, iOS 5 includes a built-in AirPort configuration utility. If for some reason you don't already have some kind of WiFi router in your home, you can buy an AirPort Extreme, AirPort Express, or Time Capsule and configure it right from your iOS device.

We imagine this feature could come in quite handy, especially for iOS users that have desktops at home or don't want to haul out a laptop when adding additional base stations or reconfiguring the network. Simply pull out an iPhone and use the configuration utility from anywhere in the house.

After four major revisions, iOS 5 will finally allow users to set custom tones (and vibration patterns) for new voicemails, new mail, sent mail, and calendar alerts. With custom alerts, you'll know right away what type of notification you are getting. If you have a household with more than one iPhone user, setting custom tones will make it easier to know which device is getting calls, messages, or has a calendar reminder popping up. BGR noted that iOS 5 includes more tone options, and will offer a way to buy new tones via the iTunes Store. (We're hoping you'll be able to add your own custom tones as well.)

We expect Apple will post a more extensive list of features once iOS 5 nears completion in the fall, and we'll definitely take a look at those features as they are revealed. Until then, let us know what feature you're most looking forward to in the comments.