i generally play with the sound on because it draws me further into the game. Also, i use an SP, and the charger is right near where i always play, so battery life generally isn't a worry for me. When im in public, i keep the sound off to avoid annoying others, though.
I find sword of mana to be very... different than any other RPG i have ever played. If you don't mind that a few of the quests are frustrating, then its a great game, and i do recommend it.
my first game (of which i have many fond memories, but sadly, have overplayed to the point where it is no longer fun) was Advance Wars. I still remember how cool it felt the first time i built a bomber...
at one point in pokemon gold (before my cartridge malfunctioned and deleted my save) i had a lvl. 93 feralgator and a team of high level 70's including a dragonite, houndoom, ampharos and tyranitar