“Two and a Half Men” — propelled by months of hype and aided by an absence of scripted competition — opened to monster ratings Monday night for CBS, including the best demo score for any regular half-hour comedy in more than six years.

But where does “Men” go from here? Big opening-night curiosity was expected — though Monday’s numbers far exceeded expectations — and a better gauge of its long-term chances with Ashton Kutcher instead of Charlie Sheen probably won’t come for another month or so.

But the show could lose more than 50% of its audience next week and still be among the top shows on television.

Elsewhere on the opening night of the season, CBS used “Men” to launch comedy “2 Broke Girls,” which delivered huge numbers of its own before it slides down to 8:30 p.m. next week. The net’s “How I Met Your Mother” also had its best premiere ever, as the Eye comedy block seemed to benefit from facing reality contests on ABC, NBC and Fox.

Monday also saw declines for ABC’s “Dancing With the Stars” but gains for its drama “Castle,” while NBC’s “Playboy Club” was pretty much a bunny-flop in its bow. CBS easily won in key demos while “Dancing” put ABC on top in total viewers.

Looking at the Nielsens, Kutcher’s bow on “Two and a Half Men” averaged a 10.7 rating/25 share in adults 18-49 and 28.74 million viewers overall — more than doubling its premiere demo delivery from last season (4.9/12). The previous highs for the long-running show came in May 2005, when it followed the “Everybody Loves Raymond” series finale with an 8.1 demo rating and 24.2 million viewers overall.

In fact, the “Raymond” finale is the last regularly scheduled half-hour comedy on any net to deliver bigger numbers than Monday’s “Men.”

Monday’s demo score is the best for any primetime entertainment telecast since the Academy Awards in February and tops every episode from last season’s “American Idol.” It’s also the biggest for a season/series premiere of a scripted entertainment series since ABC’s second-season opener of “Desperate Housewives” in September 2005.

The big showing at 9 p.m. for CBS provided substantial sampling for the premiere of half-hour “Two Broke Girls” (7.1/16 in 18-49, 19.37 million viewers overall) at its special 9:30 p.m. time before it shifts to its regular, earlier slot. “Broke Girls” beat ABC’s “Dancing” by 7 shares in adults 18-49 and gave CBS its best showing in the timeslot since “Men” in May 2005; it also drew the largest overall aud for the series premiere of a fall comedy since NBC’s “Inside Schwartz” (airing behind “Friends”) in 2001.

ABC’s “Dancing” (4.0/10 in 18-49, 19.03m) was down 22% from its premiere of last fall but was a strong second in demos to CBS from 8 to 10. And 10 p.m. drama “Castle” (3.2/8 in 18-49, 13.28m) was up 19% from last year for its best preem score to date.

“Castle” and the second-season premiere of CBS’ “Hawaii Five-0” (3.4/8 in 18-49, 12.19m, down from last year despite the big lead-in) made life difficult for competing 10 p.m. NBC drama “The Playboy Club” (1.6/4 in 18-49, 5.03m), which had a modest premiere on what has been a tough night for the net. One year ago, the series opener of “Chase” did better for NBC (2.3/6 in 18-49), but it had a stronger lead-in.

CBS opened with the best premieres score yet for “How I Met Your Mother” (4.7/13 in 18-49, 11.01m at 8 and 5.2/13, 12.22m in a special airing at 8:30), which easily led its hour among young adults and provided the net with roughly 45% time-period improvement over last year’s openers of “Mother” and “Rules of Engagement.” For the night, CBS prevailed over runner-up ABC by 5 shares in both adults 18-49 and 25-54.

Fox went with the season finale of summer series “Hell’s Kitchen” (2.6/6 in 18-49, 5.99m) and finished third among the broadcasters for the night in 18-49. The net bows dinosaur drama “Terra Nova” next week, and veteran drama “House” returns the following week.

At NBC, “The Sing-Off” opened to a 1.9/5 in 18-49 and 5.3 million viewers overall from 8 to 10 p.m. — lagging the competition but the best non-sports demo delivery in the time period for the net since mid-January. Compared to last year’s opening night, when it was boosted by good series premiere scores for “The Event,” NBC was down about 30% in 18-49 (1.8 vs. 2.6 for the night).

“The Playboy Club” will be rebroadcast Sunday afternoon on NBCUniversal cabler Bravo. The move was pre-planned, not a reaction to the low numbers the drama scored Monday night. NBC, in fact, said it had no last-minute marketing or promotional plans to help spruce up next week’s “Playboy” episode.

(Stuart Levine contributed to this report.)