It started out with a wow factor: will.i.am, Taboo, Fergie and apl.de.ap descended from atop the stadium, outfits glittering, bedazzled outfits, singing (with the help of auto-tune) the party anthem "I Gotta Feeling" with hundreds of dancers grooving in step on the field.

But the Peas didn't match the energy of the song; they seemed tentative, and tense. It didn't help that Fergie's mic didn't kick in until she was midway through her first verse.

If the explanation for the Peas' flatness was nerves, those nerves never settled, as they plodded through such songs as "Pump It" and "Boom Boom Pow." Technically, they were fine -- Fergie's voice soared, the raps were performed right. They didn't excite. Even former Guns 'N Roses guitarist Slash seemed bored as he joined Fergie for a short snippet of "Sweet Child O' Mine," an unnecessary cameo that failed to add any sizzle to the set.

So it fell to Usher to breathe some life into the halftime show, and he didn't disappoint as he appeared in all white with a flank of dancers. Although Usher seemed to dance more of his No. 1 hit "OMG" with will.i.am than sing it, his syncopated moves and flips provided the energy jolt that the Peas lacked.