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In my experience (2G, 3G, 4S, 5), the glass holds up really well. Any small scratches that do occur aren't noticeable when the screen is on.

As far as resell value, I've never gotten less money for having a phone with minor scratches on the screen. I list it as near mint, and no one has ever complained when they saw it in person.

You have had some good luck, I wouldn't consider an iPhone with scratches near mint, maybe good condition depending on the amount and size of scratches along with asking price of the phone.

Of course in my area, there is alot of dust and dirt blowing around which causes scratches almost instantly.

I have used the ones from Verizon and they seemed to hold up well.
 
Looking at my 4S there isn't any rainbow effect even with oily residue showing up. There might be under certain light condition but I haven't seen any rainbow effects. It's just surprisingly good for $1 and the touch screen response is the best I've seen out there. Bubbles go away if you push them out and comes with a cleaning cloth.

Is the Dollar Store different from the 99cent Store? It was the 99cent Store that was close by me thinking it was the Dollar Store. There's also a store called the Dollar Tree. I don't go to these stores, so I''m not sure which to go. I'll have to yelp the closest Dollar Store and get to one this weekend.
 
Is the Dollar Store different from the 99cent Store? It was the 99cent Store that was close by me thinking it was the Dollar Store. There's also a store called the Dollar Tree. I don't go to these stores, so I''m not sure which to go. I'll have to yelp the closest Dollar Store and get to one this weekend.

I got mine through Dollar Tree but is believe any generic dollar store will work.
 
In the Atlanta area I go a store called Five Below. They have them for the 5 and up and work great. I think this store is in several states.
 
Without a doubt my vote is for Anker. Cheap yet great quality, great warranty and great customer service.
 
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