I have had my Ion for two days now. The screen is pretty bright, and there is really no need to crank it up to 100. I have actually found it pretty tough to drain. The first day I spent several hours setting up the phone I wanted (Phone was at 60% battery), and about 4-5 hours laters of pretty heavy use, I was down to about 5%. My second day, which I finally had full charge, I had to get creative on how to run down my battery. I know it's not a good thing for your batter to die, but I only plan to condition the battery two times. My second day was even tougher to kill the battery. I played music for roughtly 4 hours at work while surfing the web and texting (150 texts or so; I am a heavy texter), played games when I got home, played words with friends throughout the day, set my screen brightness to 100% for roughty 2.5 hours when I got home, and the battery didn't die until around 7. So I got around 10-11 hours of use for moderately heavy use the second day. Android is a power hungry OS so don't expect to get ridiculous battery life like on a Blackberry. To conserve battery life, just check how often things sync, set your screen to a reasonable brightness, turn off gps and bluetooth, and get on a wifi network when you're near one.
I agree with every owner who says that the reviewers are a bit harsh on the Ion in their reviews. I think it is a superb phone, and one that will last me a lot longer than my little Aria did. That thing was a fighter though. Loved CM7 on it. The call quality on the Ion is good, the call volume is significantly louder than my Aria (it could be a tad louder but I dont mind), I have hardly had any hiccups on the phone, and it feels pretty dang smooth compared to the Aria. There's always going to be a next best thing out there. The One X and SGSIII will probably be "outdated" no more than 3-5 months. Know what you're paying for and you can be happy with your purchase. I know I am. I bought the Ion at Best Buy for $50, it comes with an 8 GB microSD card, albeit class 2 but its free, and you are eligible for 50GB of free cloud storage through Box (not dropbox). The camera is phenominal! Don't expect to compare the pictures to the quality to that of an actual camera, but it is crazy good for a phone. The quick launch of the camera is nice too. My only concern is if no one will find a way to unlock the bootloader. I can live with it, but I would rather have an unlocked BL and root. That's my two cents. Definitely a steal of a phone.