1) Android L is more colorful and vibrant. There is a more pronounced use of colors in the Launcher and all the apps, that Google has updated for L. The fonts look crispier and neat.
Redesigned Launcher: Animations are more fluid and appealing. Apps drawer now opens up like the folders pop up, without a transparent background. Google Now is more colorful and beautiful.
2) More feedback for every touch, the screen vends out ripple like effects for all your touches and it's beautiful.
3) Revamped Quick Settings : Quick Settings work twofold now. One slide down and you get only your notifications. Another slide down and you get quick toggles for WiFi/data/location and flashlight (new).
4) Notification on lock screen. You can now enable notifications to be seen directly on your lockscreen, even access your quick settings from the lock screen. You can also set Priority Notifications using your device's volume button, only certain notifications/people will be able to get through.
5) Multi-user support: Want to give your phone to a friend to check out, but don't want him to look at your stuff? Switch the phone to guest mode and you are done. You can even create multiple profiles on the phone and switch between them. Each profile will have its own set of apps and data.
6) Battery Saver Mode: The battery saver mode is in built now and provides incredible improvement. It downgrades the performance of the device, but extracts that every extra bit of juice from the battery it can. The status bar and the bottom bar become red when the battery is below 15%.
7) Dialer and Phone calls: Phone calls now come up as toasts over your phone, in case you don't want to be disturbed while you are doing something on the phone, you can swipe away the notification. (Earlier while you were getting a call, there was no way to do this.). Dialer is improved, more colorful and interactive, to go with the overall theme changes. You can even pin your most used contacts directly on your home screen now.
8) Recent Apps: The recent apps now show up as a deck of cards. One app can have multiple entries, for e.g. different chrome tabs will show up as different entries in recent (after chrome is updated).
9) Security
i) Smart Lock: You can now pair your phone to a trusted device (You car's bluetooth/your smart watch etc) and the phone won't ask you for the unlock code/pattern. Same is the case with trusted face.
ii) Encrypt Phone: There is an option to encrypt all of the content of your phone (apps/data).
10) Keyboard: The keyboard looks fresh and white, more responsive and there is an option to add words to your local device's dictionary for it to be added to suggestions the next time.
11)Screen pinning: One rather unusual feature is that you can also pin one of the apps on the device and it would be locked to your screen. You can't exit that app without pressing back and recents button together and if its locked with a pin, you would need the the pin as well.
12)Performance improvement
All previous Android apps ran on Dalvik runtime. This is equivalent of Java Virtual Machine and was used to interpret Java byte code. In simple words Dalvik was what your applications run on.
Android L aka Lolipop has introduced new new runtime called ART(Android runtime) . This new layer offers very high performance compared to Dalvik.
13) Material Design
Material design is supposed to provide users with a more realistic UI effects and a 3D like interface. UI effects re made to seem more natural and less artificial which seems to be the case with modern UI's. Personally I am not impressed with it.
14)
Go to Settings, Select About Phone option , further tap 'Android Version' repetitively and when a colorful Lollipop appears on the screen. When the lollipop loads, you can tap it to change colors, or long-press it to reveal the Easter egg: a Flappy Bird clone game, made with a bugdroid and lollipops. Enjoy it guys.