This is the new notification thingy when you drag the top of your screen down. I have duplicate birthdays because its a bug and I actually fixed it yay :). Anyways it shows recent messages the current weather birthdays mail and facebook alerts for me now! I think this is the best feature so far.
In here you can see the new iCloud, which syncs all your devices calendars, notes, and contacts and whatnot its also really neat and I have a photostream set up for my itouch and my iphone so all the photos sync with each other! Twitter is also integrated into iOS5 now even though I dont really use it...
An update to Safari is the option to "Open in Background" which lets you open new links without navigating away from your current page. Its pretty awesome.
This new app is called Reminders and its slightly redundant to calendar but not really if you need to take out the trash and stuff you can put it here. Apparently you can add it to your notification center but I have yet to get that to work. All in all I can see this working out well if you want to be productive throughout your day.
Wifi-Sync!! Now I had this when I was jailbroken and its much much easier now! Instead of having to run the wifi sync app on my computer it automatically syncs. To enable this you go to iTunes and check the "Sync over Wifi" when you are plugged in. Once you unplug the cord you are still synced and every time you are near the iPhone seems to automatically sync to my macbook. Very convenient.
This is my first impressions so far but there are things I miss about being jailbroken like seeing contact pictures on my messaging app and contact list, being able to send and reply to texts on my lockscreen. And opening SBSettings to restart my springboard or reboot the phone easily. However, iOS5 does offer some fun features on the table. One I forgot to mention that is really handy is the new way to get to your camera app! On the lock screen if you double click the home button you can quickly access your Camera and use the volume up button to take a new picture! Never miss that moment again because you took forever to open Camera :).
This is the end of my impressions on iOS5. Am I going to keep it? Yeah. Next step? Jailbreak ! :D
If youre asking how I was able to test it ? I found someone with a developer's account on Reddit and asked him to add my UDID to it for free. You might be able to do the same! A huge problem I ran into was not being able to restore my backup from my jailbroken 4.1...spent a few hours trying to fix it only to downgrade to 4.3.3, backup my contacts and stuff, and then setting my phone up as a new phone under iOS5.
If you have any questions/feature requests lmk in the comments and I will update or answer the best I can ^_^