With all the original Japanese names and an extra dungeon, it still just seemed too easy.
The music is slightly off compared to the original soundtrack, but I feel that some of that may be coming from the under-powered speakers of a GBA rather than a fault on the game itself. The extra dungeon is fun, and the ability to switch out party members adds an extra challenge to the game, as to access the secondary characters challenges in the new dungeon, you have to kill the boss of the game with them in your party.
All of the secondary characters (Yang, Cid, Palom, Porom, Edward) have new weapons and armor that they can make use of, so it's not like they are stuck with the under-powered equipment that they had on when they left your party in the first place. (Or DIDN'T have on if you were quick/smart enough to empty out their inventory before they left your party for some extra gold!)
There is still the Yang HP bug, where his hitpoints get stuck around 6000. I'm not sure why that bug was developed, but I suspect since Yang had more HP than other party members, it was a quick fix to keep him from getting over the 9999 HP limit due to a quicker HP growth, since they never expected anyone to level him up past 30 or 40 at most.
The game does have some issues that make it easier... your characters randomly get two attacks in a row, which can help out a lot in sticky situations, or just speed up the fights in general.
Overall, an excellent port of one of the best games known to man.