Turning off auto-brightness in a situation where the phone is being used in direct sunlight won't help. The whole point of auto is so that it sets it to the ideal brightness depending on the light source around the phone. At severe light conditions the auto-brightness is the same as turning off the auto function.
The slight over gloss and major lack of brightness. We tend to think the difference isn't great between competing phones, but in fact they are. One of the things I look at laptop screens when buying are brightness, color, viewing angles. For a windows laptop Mid ~300 to 400 nits are good standards, but they are average if not low for high quality/flagship phones. The iPhone 4/4s has a max brightness of around ~500nits while One X has ~550nits. The S3's is ~330nits. So it's good using in almost all indoor conditions but struggles in the sunniest times.
After Jelly Bean the stock email app also has a severe blue tint/low brightness issue like the stock browser. It is highly recommended to switch to a different browser, can't say about email app.