For me, I picked up the GS3 to try and use while I waited for the new iPhone to come out. This would allow me to sell my iPhone before the market got flooded.
Here are my thoughts:
First, I am surprised that I really like the phone as a whole. The screen is amazing, I do not think it is too big. Swipe to text makes it easier to type with one hand versus the iPhone IMO. I love having the local weather built into the clock on my home page. Some of the widgets are pretty nice.
I like the GS3 because it is different. It is nice to have a change.
BUT...
There are several things that annoy the crap out of me. The swipe to text is really annoying from time to time. For example, it won't come up with easy everyday words like "your" "got" "did" "does" "food" "he" "out"... It kills me when it does that crap. There are times where the screen will show the swipe on the keyboard that I made, yet no word will show up. Sometimes it happens several times in a row or throughout one message.
My car has a factory iPod/iPhone hook up giving me in dash control of my phone. With the GS3 (assuming I took the effort to put my music on it) would require and AUX cable and I would have to pick the music on the phone itself, which is unsafe, so I pass on that.
My notes through iCloud sync to my iPhone, iPad, and MBP... which is nice... not to mention my contacts and everything else.
Safari in iOS is much smoother to use than the standard browser on the GS3 IMO.
Ice Cream Sandwich is still choppy from time to time (I hope Jelly Bean releases for it before the new iPhone comes out). It also bothers me how JB has been out for a while, yet it takes a long time (and sometimes never) for a phone to get updated to the new OS.
Ever since I customized the home screens to my liking with some widgets, the battery life seems to have fallen drastically.
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In the end, I really do like the GS3. And I was surprised that I liked it considering how much I hated the GS2 when I had it for work.
However, I have no plan on keeping it. And even though I am disappointed (as of right now) with the purported "Taller" new iPhone. I am invested in the Apple ecosystem, and I still prefer iOS to android.
Hopefully, the new iPhone that is revealed next week is a little more polished than the leaks we have seen (or different all together, which I doubt), and that the phone grows on me once I have it in my hands.
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I also wanted the GS3 but someone sold me a brand new unlocked international one x for $300. And this enabled me to use the non smartphone data plan on att and drop my bill by 20 bucks.
Thats a pretty sweet deal.