Galaxy S4 is  an incredible phone. I have been using this unlocked S4 for past 2 days helping a friend to migrate from iPhone 4S. My friend has been on iPhone and it also gave me a unique perspective. I used iPhone for couple of years and been using Android for past 3+ years.I have used Galaxy S3, Note II and for me S4 is more like a S3s :) If you have a Galaxy S3, it is perfect and there is no need to move to S4. The new features are more like minor upgrades for me. Just like Detroit rolls out new cars every year, phone manufacturers have found excellent way to make yearly upgrades.Battery came for almost a day. The video playback was crisp and my friend was amazed at the customization options. It is heaven for a iphone user to come out of shackles and explores the wonderful world of Android. It sure sounds like it is for geeks, but Samsung has created lot of ways to simplify and make it less intimidating. The EASY mode is for one such reason. Samsung''s addition of all those apps (commonly referred as crapware) is not as bad as HTC or LG. Android experience is classified as pure vanilla in phones like Nexus. Vendors like Samsung have added a whole lot of extra programs.5" HD Super AMOLED 1920 x 1080 display  (441 ppi) is just plain gorgeous. 13 MP camera takes ginormous image sizes. I put a 64 GB microSDXC card  SanDisk 64GB Mobile Ultra MicroSDXC Class 6 Memory Card with SD Adapter - Retail Packaging as my friend wants to take lot of movies (built-in 2 GB RAM, 16 GB ROM). No stuttering, and very smooth playback of videos captured in varying light conditions (HD Playback; HD Recording). Compatible video types are AVI/DIVX, WMV/ASF, FLV, MKV, MP4/3GP, WEBM. HDR and Panaromic photos were incredibly sharp. Compatible audio types are:  AAC, AMR, MP3, OGG, WMA/ASF, 3GA/M4A, FLAC, WAV. Google Music, PlayerPro Music player are producing excellent music.  Audio/Video is one section where S4 has nudged S3. For a normal user, if you are not into lot of video processing this does not matter.S4''s infrared sensor is the same technology as TV remote control, so with WatchON you can change the TV channel from your phone. My friend was shocked to see this feature. Having used Android for a long time, I explored all new features one by one. My friend is still getting used to and feels this is too complicated. I broke down into lot of sub features and told my friend he may not use 50% of features, but told him to explore one feature at a time and focus on that.Games were very buttery, this phones runs ARM®-based octa-core mobile CPU. This is apparently world''s first!  Inside this chip is Imagination Technologies'' PowerVR SGX544MP3 GPU. I tried several car racing games and performance was phenomenal. People on the XDA-Developers forum report seeing smearing and ghosting when scrolling on the phone. This especially occurs to people when scrolling among darker colors, which begin showing up as purple. I tried hard to see if I could on the S4 I was testing with my friend and I could not see it. I am sure these can be upgraded with software over due course.Air View and Air Gestures - are they worth it? Air view is similar to how the S-pen on the Galaxy Note 8 works. Simply hover finger a few millimeters above the screen and in supported apps, you''ll see a preview of content. This works with many of Samsung''s built-in apps, including the photo gallery, the dialer, Samsung''s browser and email client. It also works with Flipboard. Air View works by cranking up the capacitive sensor on the screen. Another new feature is Air Gestures. This uses the IR sensor on the top of the phone to detect movement by your palm or finger. One can flip between open tabs in Samsung''s browser app, skip to a new song in the music player and do many other things. I say these are still in works and sometimes not very efficient.GPS was spot on and I tried multiple GPS apps. It was bright outdoors (had to crank the brightness all the way up). I tried multiple apps to demonstrate to my friend. In the end, my friend was impressed with what all Android and in particular S4 had to offer. Smooth and Stunning display!I tried following apps and they just worked awesome.Amazon MobileAndroid StatusAndroidifyAngry Birds (Space/Seasons)Asphalt 7Amazon App StoreBoxCar Maintenance Reminder ProChromeCNET TVNAVIGON (from Garmin - offline maps)Google Navigation/Earth/MapsGoogle Currents (nice way to read News)Draw SomethingGoogle DriveEbayLinkedinGoogle MusicTapatalk (awesome forum browsing app)OverDrive Media Console: Library eBooks & Audiobooks (public library consumption of media)Microsoft One Note (legacy docs, skydrive of 25 GB is good)Subsonic Music StreamerTerminal Emulator (still need to use vi, yes this is it)TweetCaster Pro for Android (excellent twitter client)Twit.TvGoogle VoicePlenty of WidgetsAsk questions, the review cannot do justice to Galaxy S4. I will be glad to answer any questions.