Good , but not great. Not to damn with faint praise, but that's the story of last night's opener of U2's four-night run at the FleetCenter. The Irish heroes delivered a subtly powerful sound-and-light display - and a proud-as-ever song list - but they didn't sustain their usual energy peaks, partly because singer Bono was clearly babying his voice, either due to a spring cold or the accumulated road rot of touring the United States for the past two months.


U2's engine was in strong order - as guitarist the Edge, bassist Adam Clayton, and drummer Larry Mullen Jr. stepped up their roles - but their front-man pilot, Bono, couldn't match them, which is highly uncharacteristic. Instead of the normal, over-the-top Bono, whose energy usually can power a small city, we heard a Bono who was hanging back and being careful not to throw his voice out. He didn't attack the songs as he typically does.


It was still an impressive show - and the sold-out crowd of 18,800 fans shouted themselves hoarse by night's end - but it was not up to the opening show in Miami in late March. Or, for that matter, up to many of U2's previous gems in Boston, which has long been one of their favorite cities since debuting at the Paradise club in the late '70s ( a memory that Bono recalled last night).


Perhaps there might have been some tension, too, because HBO was there last night (a crew of 92 people, no less) to tape the show for an upcoming special. The cable network will also be on hand at tonight's performance.


U2's precision and Bono's guile still carried the night, from the opening ''Elevation'' (with the house lights on, fosterng an immediate intimacy), the euphoric radio hit ''Beautiful Day,'' the crunching, Edge-dominated ''Till the End of the World'' (with Edge and Bono out on the heart-shaped catwalk that went to the center of the arena), and the elegant ''She Moves in Mysterious Ways,'' followed by a snatch of the Beatles' ''My Life.'' (Bono later improvised on Bob Marley's ''Get Up, Stand Up,'' but didn't perform the Ramones tribute he often has on this tour).


The band followed with some new songs - ''Stuck in a Moment that You Can't Get Out Of'' (a Memphis-like soul ballad), the understated ''Kite,'' and the street-rocking, Lou Reed-like ''New York,'' with Bono singing about ''how the Irish have been coming here for years.''


Two groups of fans offered him an Irish flag to hoist aloft at this point (as he sometimes does), but he declined.


U2 then romped down memory lane with the chiming psychedelic rocker ''I Will Follow'' and all-time anti-war classic, ''Sunday Bloody Sunday,'' which drew the night's loudest response.


Bono took a break to address the crowd about the group's oft-quoted desire to be ''the best band on the planet.''


The remark has drawn criticism - does U2 really need to hype itself this way? - but as Bono said, ''You know where that's coming from, don't you? It comes from being Irish. ... Irish people are not cool; Irish people are hot. That's where that's coming from.''


U2 valiantly hit the home stretch with ''Desire'' (with all four members on the catwalk, as Mullen played a Bo Diddley beat on a single drum), a touch of Van Morrison's ''Gloria'' (give us more), and a spiritual closing of ''Where the Streets Have No Name'' and the Martin Luther King tribute, ''Pride (In the Name of Love).''


The encores included a rampaging ''Bullet the Blue Sky,'' and raps by Bono against handguns and for unity with ''African brothers.'' His politics were intact, even if his voice needs to heal.


Opener P.J. Harvey delivered an exquisite set of tough-as-nails, punk-influenced rock, but it was a shame that so few people had yet arrived to hear her. U2 fans should be more supportive than that