First matches as a kid were stood on Bramall Lane terrace. Then it became the away end. Unfortunately, my dad and his mates didn't know this (god knows how not) and I'm sure I remember for the first match after having to climb into the South Stand. Must have been about 7, so might be wrong.
Then stood on the kop for many years and sat on it, but finally got hacked off with being rained on, sun in eyes etc. and moved to South Stand with some mates about 6 years ago. Gangway G so a bit of atmosphere, especially for the bigger games, and I wouldn't go back. My 10 year old has had a season ticket with us for the past 4 years, and I've never been tempted to ever consider the kop again. Must be an age thing, but quick entry and exit and the ability to get to the bogs / refreshments easily is great, plus the seats actually have some leg room and the view is miles better.