Let the cynics talk. Tom Cruise (search) is in love — and he just can't restrain himself.

"You know what? There's always cynics. There always has been. There always will be," said Cruise, who hasn't been shy about displaying his affection for "Batman Begins" actress Katie Holmes (search). "I have never worried ... about what other people think and what other people say."

Cruise, 42, and Holmes, 26, went public with their romance in April, smooching and posing for photographers in Rome. They recently became engaged.

Many have doubted the romance. The words "publicity stunt" have rained down on the couple like an alien invasion as Cruise has been busy promoting his new film, "War of the Worlds," directed by Steven Spielberg, which opens on June 29.

"I have to tell you, it's just a great time in my life," Cruise said in an interview that aired Friday on NBC's "Today" show. "I'm really happy. And, you know, I'm engaged. I'm going to be married. I can't restrain myself. It's like you've got two little cords on your mouth and you can't stop smiling."

The 42-year-old actor, whose marriages to Mimi Rogers (search) and Nicole Kidman (search) ended in divorce, declined to say what the 26-year-old Holmes has brought to his life that wasn't there in the past.

"I don't want to compare things," Cruise said. "It's that thing where you just — in life when it just happens. ... You meet someone. And it's — I can't even describe it."

When asked if he could be with someone at this stage in his life who doesn't have an interest in the Church of Scientology (search) — Holmes has said she's embracing the religion — Cruise told interviewer Matt Lauer: "Scientology is something that you don't understand. It's like you could be a Christian and be a Scientologist.

"It is a religion. Because it's dealing with the spirit. You as a spiritual being. It gives you tools you can use to apply to your life."

When Lauer mentioned Cruise's earlier criticism of Brooke Shields (search) for taking anti-depressants, Cruise told the "Today" show co-host he didn't know what he was talking about.

"You don't know the history of psychiatry. I do," Cruise said.

The interview became more heated when Lauer, who said he knew people who had been helped by the attention-deficit disorder drug Ritalin, asked Cruise about the effects of the drug.

"Matt, Matt, you don't even — you're glib," Cruise responded. "You don't even know what Ritalin is. If you start talking about chemical imbalance, you have to evaluate and read the research papers on how they came up with these theories, Matt, OK. That's what I've done."