If you haven't checked it out already, I'd suggest doing so. http://www.apple.com/ios/ios5/ It's a pretty good set of improvements. All things that definitely needed to be done. The single BIGGEST change resolves my single BIGGEST complaint with all other versions of iOS. The notification system.
Instead of opening up their OS to allow 3rd party developers stuck in Cydia, Apple pretty much took their ideas, bundled them all up, and called it iOS 5. Just about every single part of iOS5 has been done before.
- Notifications: It's a pretty clear copy of Notified (http://notifiedapp.com/) which is a pretty, but less feature packed version of LockInfo (http://david.ashman.com/lockinfo/).
- iMessages: Basically WhatsApp (http://www.whatsapp.com/)
- Camera: Now with some of the features that Camrea+ (http://campl.us/) has. The funniest part is that for a while Camrea+ was pulled from the App Store for using an unapproved API. What did they use? Volume button to take photos. One of the "new" features in iOS 5.
- Safari: They added the ability to, while your browsing something, "read it later". Sounds a lot like Read It Later (http://readitlaterlist.com/). Now of course, Read It Later had no way of integrating their app into the browser since Apple doesn't allow developers access to that like Google does with Android. So Apple did it themselves.
Reminders, and the location based reminder feature, is pretty original and actually looks very cool. I'm sure someone will make something similar for Android if it doesn't already exist.
Those are the biggest features really. I only point this out because I think that, while good features, they could have done better by just offering 3rd party developers a little more freedom on their platform. There was really no need to duplicate the efforts of developers that already have widely used applications.
Also, it should be noted that all the apps I listed have many more features than the iOS5 alternatives, so I'd still highly recommend LockInfo, WhatsApp (actually works with Android and Blackberry too!), Camera+, and a service like Read It Later. These are actually some of my favorite apps so I'm still excited to see Apple recognize that they are good. I'm also excited to see what all these talented developers will do next! I like David Ashman's (Stimpy5050) attitude in his twitter post