ATLANTIC CITY — Even professional entertainers can improve over time at their job.

When pop-R&B singer Rihanna made her casino debut here in 2006 at the House of Blues Atlantic City in the Showboat Casino-Hotel, The Press wrote that she didn't have the ability to move the crowd, and she didn't have the audience jumping the way previous pop and hip-hop visitors had done.

Rihanna's headlining appearance in the Event Center at the Borgata Hotel Casino & Spa was an improvement over what she has done in the past.

The singer's performance was helped by touring behind a new CD, "Rated R," that features edgier material.

After a 100-minute delay between opening act Ke$ha and headliner Rihanna, the Barbados-born entertainer came on stage to sing one of her best song, the single "Hard" from her latest CD.

One of the things that made Rihanna's concert enjoyable is that she took her studio recordings and added more of rock flavor to the songs by having two guitarists on stage with her, one of them being lead guitarist Nuno Bettencourt of the band Extreme. They helped energize the proceedings for the already hyped crowd.

Rihanna, 22, comes off as a more confident performer and singer frequently commanding the stage by herself even though she brought four male and two female dancers with her.

The start of Rihanna's show was very uptempo, with her hits "Hard," "Shut Up and Drive," "Disturbia" and "Rude Boy" all coming early.

Even though Rihanna is better live than she used to be, she did string too many slow to mid-tempo songs together in the middle of her show.

Rihanna, her female backup singers and two guitarists sat on her pink tank to sing an acoustic version her duet with Ne-Yo, titled "Hate That I Love You." Her backup singers did a good job of recreating the harmonies from her song "Rehab" live. The album cut, "Stupid in Love," was the best of the slower material.

Rihanna singing the line, "I still love you, but I just can't do this," took an extra meaning as her face filled the video screen with everyone in the audience knowing that she was physically assaulted by her former boyfriend and fellow singer Chris Brown. During the same song, she sang the line "I may be dumb," inserted a dramatic pause, and then finished with "but, I'm not stupid in love" with her wagging finger in closeup in the video screen.

After all the slower songs, the energy zoomed up with Rihanna singing her hit "Don't Stop The Music," which featured her most daring, body-hugging outfit of the night. It was flesh colored with white vertical and horizontal lines. "Don't Stop The Music" was a crowd pleaser with Rihanna encouraging the crowd to jump, and one of her male dancers spinning on his head on stage.

Two of Rihanna's lesser-know songs were among the highlights of the second half of the show as "Breakin' Dishes" and "Let Me" fit well in between smash hits "Don't Stop The Music" and "S.O.S."

By changing and taking risks musically from tropical sounds to more urban and European dance-pop and darker material, Rihanna has pulled ahead of her pop-R&B contemporaries, including Ashanti, Cassie and Ciara.

It's still too early too tell whether Rihanna's opening act, Ke$ha, 23, has more to offer than her drunken, party girl act. She did make for a good opening act for Rihanna. She sang her three hits, "Tik Tok," Your Love Is My Drug" and "Blah Blah Blah" and other songs from her debut CD, "Animal."