Apple will be finally releasing their most eagerly awaited next generation mobile operating system – iOS 5 tomorrow, October 12th, which includes more than 200 new features for iPhone, iPad and iPod touch.

We have compiled a list of our top 25 features in iOS 5, including some of the hidden features.

We’ll try to keep this list of features as brief as possible and provide a link wherever possible for more details about the feature.

1. Revamped Notification system with Notification Center, Lock screen display and lots more – more details here and here
2. Siri – Apple’s new intelligent personal assistant that is currently exclusively available only on iPhone 4S – more details here and here
3. Integration with iCloud – Apple’s new Cloud based service
4. iOS 5 includes two new features that will allow Apple to finally cut the cord and usher us in the post-PC era. The first one is PC Free – more details here
5. The second one is Wi-Fi sync, will sync and backup content such as movies, TV shows, home videos, and photo albums from your iOS device to your Mac or PC whenever its using the same Wi-Fi connection and the iOS device is connected to a power source – more details here
6. iMessage – Apple’s new messaging service For iPhone, iPad And iPod Touch users – more details here
7. iOS software updates can be downloaded over-the-air (OTA). The iOS software updates will be delta updates, so instead of downloading the entire OS, you just download what has changed. This probably falls under the PC Free feature, but in our opinion this is one of the major new features of iOS 5. Video
8. Earthquake Early Warning Notifications For iPhone Users In Japan – more details here
9. Improved Camera app – more details here
10. Improved Photos app – more details here
11. A new Reminders app that allows you to store list of things to do that can be associated with a date and also assigned to a location – more details here
12. A new Newsstand app that essentially organizes your magazine and newspaper app subscriptions in one place to access them easily and quickly – more details here
13. Twitter is deeply integrated in iOS 5 and several apps including Camera, Photos, Maps, and Safari – more details here
14. Mobile Safari gets a number of new features such as Reader, Reading List, full tabbed browsing for iPad users and ability to tweet from Safari – more details here
15. Mail app gets a number of new features and improvements such as rich text formatting, ability to flag important messages, access to built-in dictionary etc. – more details here and here
16. With the improved Game Center app, you will be able to add your photo to your Game Center profile, see friends of friends, compare yourself with your friends with Achievement points per game and lots more – details here
17. AirPlay Mirroring for iPad 2 – more details here
18. New Multitasking gestures for iPad – more details here
19. AssistiveTouch feature that allows you to use your iOS device if you have difficulty touching the screen or if you require an adaptive accessory – more details here
20. Nitro Javascript Engine Performance Improvements To Home Screen Web Apps – more details here
21. iOS 5 also brings number of improvements to Calendar app such as ability to see year view on the iPad and week view on the iPhone and iPod Touch, ability to view event attachments directly within the Calendar app and other iCloud features – more details here
22. FaceTime – Apple’s video calling feature gets number of improvements such as improved video quality and FaceTime calls over 3G – more details here and here
23. Download multiple apps simultaneously over Wi-Fi And 3G – more details here
24. Weather app also gets a number of improvements in iOS 5 – more details here
25. Music App gets some minor improvements – more details here

Bonus feature:

• New First Boot Animation – more details here

You can checkout the video by Apple introducing iOS 5:

If these new features and improvements are not good enough and you want to jailbreak iOS 5 then checkout the latest status update on jailbreaking iOS 5 here.

TechZoom has done the laborious job of compiling an exhaustive list of most of the 200+ features, follow this link to check them out.

Update 1:

We should have included these features:

• iOS 5 now allows you to set custom tones for tweets, voicemails, emails, calendar and Reminder alerts
• You can create a shortcut for a word or phrase via Settings->General->Keyword->Add New Shortcut

We may have inadvertently missed out a major feature in our top 25 features list so please feel free to point it out in the comments and don’t forget to let us know which are your favorite features.