I tried to post this as a review, but it was not accepted. Just so it does not go to waste and maybe turn up in search, post here in the forum.
There is some confusion as to what is "Nusa Dua Beach." Nusa Dua is a large planned resort (also known as BTDC - Bali Tourist Development Corporation), that faces three distinct beach fronts: (1) South, from Geger Temple to the Grand Hyatt, called Geger and Mengiat beaches (2) Center, between the two "islands" (really rocky points called Dharma (north) and Gede (south), and (3) North, from Melia Bali to Club Med. The beach and resorts north of Club Med are off of the Nusa Dua BTDC resort property and properly called "Benoa." Really, its the same beach as Nusa Dua North.
Overall, the beach at Mengiat has not changed. It is still as described in the previous reviews: beautiful while sand, wide beach, well maintained by the luxury hotels. Yasa Segara village cooperative is still operating their beach cafe, where reasonably priced food and drink is available, as well as serviced beach chairs. Mengiat is accessible to anyone without the need to stay in a nearby luxury hotel and is most easily accessed from Jl Pantai Mengiat, straight down through the stone gate and dirt road alley to the free beach parking lot. The hotels with beach front at Mengiat are the Grand Hyatt, Ayodya, Novotel Nusa Dua (not Novotel Benoa), Amanusa, and St Regis. Inna Puri Bali Hotel is closed for renovation.
At this writing, Geger Beach, at the extreme south, is a disaster, and should be avoided. There is a massive construction project underway for about a 1,000 room hotel and luxury villas that will dominate the entire Geger Temple area when complete. The local Geger village cooperative cafe is still in operation, but most of the other beer cafes have been closed and the beach chair rentals have been clustered in front of the cafe. No more topless sunbathing. It appears the land to the north of the cafe and next to St Regis is being prepped for construction as well. The beach at St Regis is fine and well maintained not affected by the construction.
The remainder of the south beach, called Mengiat, is vey nice. The best location is right in front of the Ayodya at Yasa Segara beach cafe, the Novotel beach club and Amanusa beach club. Amanusa has my vote for most private and luxurious beach club at Nusa Dua.
Other news: The Bali Golf Course at Nusa Dua has been closed and site prep is underway for a new hotel (Shangri-la branded) to be located behind the Amanusa beach club. Future noise and dust hazard I believe.
The center area, between the two "islands" has been developed into a resort property called "The Bay." All the small warungs have been run out and the area is monitored by a tourist police post next to the Melia Bali Hotel. This area is not really a beach, but a tidal pool. At low tide, the bottom between the islands is partially dry and its possible to walk out into the tide pool area. Overall the center area is cleaner than ever, but not as local after the introduction of The Bay resort. This is not really a beach, although some reviews refer to it as so.
The north area is a narrowish strip of sandy beach that faces directly east. The beach is most narrow at the hotel strip Melia Bali, Laguna Resort, Westin Resort and Nusa Dua Resort. However, all of these hotels maintain a very clean well managed beach area, so no disappointments. At the very north end of Nusa Dua, the Club Med has a very private and wide beach area, one of the finest on Bali. My vote for second best beach club in Nusa Dua.
North of Nusa Dua to Benoa the narrowish strip of beach continues all the way to the the Novotel Benoa Resort. One of the nicer beach areas is at the Conrad Hotel. The further north, the more impact from the water sports vendors and lots of boats anchored off the beaches.
For the most part, the hotels are careful to maintain beaches in good condition and safe. Most put buoys in the water to prevent guests from swimming out too far. Almost all hotels have morning beach groomers and pick up flotsam and trash that comes ashore overnight.
One final note - Bali does have distinct seasons, and the nature of the beaches can change dramatically depending on the season. For example, winter season brings heavy rain which means ground water runoff into the ocean which results in "brown water," and is gross. Winds generally blow from the east in summer, thus more seaweed and flotsam at Nusa Dua, and from west in winter, thus lots of flotsam and trash wash up at Jimbaran, Kuta, and Seminyak.
There is no "perfect beach," but Mengiat at south Nusa Dua is about as good as a beach can be.
Biggest problem on Bali right now is lack of infrastructure and traffic jams. So stay on the beach longer and avoid the traffic nightmares on Jl Bypass!!