Been a season ticket holder in 124 for two seasons. Great way to spend a weeknight when there is nothing else going on during the winter months. I love having 41 games a year to look forward to although I don't get too attend every game.
Higher up is definitely better if you opt to sit in section 124. I would say rows 12 thru 20 would be the most ideal because you sit down next to the floor and it's a challenge to see what's going on at the opposite end of the court. The corner is far from the best angle but you should avoid the upper arena at all costs at the Oracle. Part of the ceiling will block your view of the opposite side of the arena which isn't a tragedy but it limits what you can see.

Riding the BART to the area is the most practical way to see an event at the Oracle and it will keep your wallet a little heavier. For concerts, the accoustics are pretty piss poor. If you hate big crowds, you will want to avoid this place because it's one of the bigger NBA arenas and they usually draw a pretty good attendance for games. You won't regret sitting in section 124, take it from me.