How's this for a tongue twister: ''When success is equated with excess/The ambition for excess wrecks us.'' Lines like that typify Switchfoot's sixth album, in which the San Diego band sounds downright desperate to say something meaningful (sample song title: ''Faust, Midas, and Myself''). Ignore the lyrics, though, and Oh! Gravity is surprisingly fun: Switchfoot have vastly expanded their stylistic palette, moving from leaden post-grunge into Stones-like swing, jittery post-punk, and, with ''4:12,'' a better R.E.M. song than R.E.M. have made in years. B-

