We were all a little nervous yesterday, weren't we?

It was opening night for Britney Spears's splashy new Las Vegas residency, "Piece of Me." Was the 90-minute concert at Planet Hollywood going to continue Spears's "Work Bitch" pop-diva renaissance, which is to say feature a Spears with life in her eyes, spark in her performance, and a little bit of the joy we've been missing? Or would the ambitious production mark a regress to the last memorable time Spears performed in Vegas, that infamous somnambulant and sad "Gimme More" disaster at the MTV Video Music Awards?

The reviews are in, and it seems Britney is back. At least, Britney is not embarrassing herself. And that's about the most encouraging news anyone could have hoped for from her Vegas show. Even better, much of the production is apparently very good.

"Spears’ mission in a nutshell: to turn a cavernous 7,000-seat amphitheater into a raging nightclub," wrote Marco della Cava in USA Today. "Mission accomplished."

"Piece of Me" is a 21-song salute to Spears's nearly two-decade-old career, with the pop supernova whirling through an aggressive onslaught of her biggest hits, essentially ensuring that no one who coughed up dough to see classics like "Baby One More Time," "Oops!…I Did It Again," "Stronger," or "Circus" leave disappointed. The night was so heavy on We Love Britney nostalgia that the singer even donned her famous body-glitter nude bodysuit to perform "Toxic."

"The show's production values are unusually high for a casino residency, often calling to mind the golden age of music videos," wrote Hannah Dreier at the Associated Press. Eye candy abounded, with acrobats, Cirque du Soleil-like performers, taut-bodied dancers, confetti, pyrotechnics, seven costume changes, and two wigs whirling through the stage at various points. At only three times during the show—including when Spears flew through the air with fairy wings for a performance of "Everytime" and during a heartfelt rendition of her new single "perfume"—did the audience bother, or even want to, stop dancing and take their seats.

Was she singing live? Well, maybe. Possibly. It seemed so. Sometimes. Heck, let's give Brit Brit the benefit of the doubt.

"Her voice didn't miss a beat," Sophie Schillaci at MTV reported. "That's not say her vocals weren't live. At times, her sweet voice shone through the backing, or we could hear her catching her breath between numbers." Planet Hollywood officials admitted that Spears is actually singing along to a backing track, to allow her to get through physically demanding segments of choreography.

The rousing response to that from fans in attendance: who friggin cares?

"With a performance this heavily focused on athleticism, asking a singer to deliver pitch-perfect vocals with no digital assistance is a bit like asking an NFL running back to run for 10 yards while carrying a tune—all game long," wrote della Cava. "This wasn't Ella Fitzgerald with a pianist, it was a pop star brining to life the songs we crank up in the shower or at the gym. It was about the raunchy sizzle of it all, not a virgin vocal."

The choreography was so fast-paced and intricate that there was even a bit of a rush when live vocals were heard, as they were in "Me Against the Music," over the backing track. "There was a certain thrill in actually hearing Spears breathing into the microphone—however infrequent," wrote Keith Caulfield at Billboard.

Katy Perry, Selena Gomez, and Miley Cyrus were all in attendance for opening night, dancing and singing their hearts out to Spears's hits—a bit of an adorable reminder that before any of them kissed a girl, came and got it, or twerked, Britney Spears was the reigning pop diva of the industry.

There was a lot that people, fans especially, were hoping for from "Piece of Me." There was also a lot that people were expecting—and, frankly, not all of it good. Shrewdly carving herself her own younger, dance-heavy niche on the strip alongside Celine Dion, Elton John, and Shania Twain and serving spectacle, nostalgia, conviction, and that spark we've missed so much, Spears appears to be serving up most of what fans hoped for with only the good parts of what they expected.

"If you're looking for a powerhouse vocal performance in your Vegas entertainment, head over to The Coliseum for Celine Dion, writes Schillaci. "But Britney fans will find no better show on the strip than 'Piece of Me.'" Duh.