I'll state my bias right off the bat. Baseball (and softball) should be played with wood bats for three reasons:
1. Safety--Pitchers, as well as players and coaches at first and second base, are at the mercy of line drives accelerated to dangerous speeds by metal and composite bats.
2. Style of play--If you can propel the ball into the air, instead of at the heads of infielders, it's likely to go deep. Compared to wood bats, metal and composite bats produce more HRs and other extra base hits, cheapening them and changing the nature of The Game.
3. Professional leagues--If pro baseball uses wood bats, why should college players use metal and composite bats? In a game that emphasizes statistics, how can college stats be meaningful when driven by metal and composite bats?
The NCAA appears to be drawing the line at composites, but I wish they'd go all the way and ban metal bats, too.