Town of the three beaches
Whether Datça is a gem and a secret, or a poor version of the grander resorts in the region, is very much up to each visitor to decide.
I did not like the place, it is too big to be one of those isolated, tranquil villages (like Selimiye (90 km) and Bozborun (100 km), or even Turunç (105 km), yet too undeveloped to match Marmaris (85 km) and Içmeler (95 km). (All destinations east.)
What is good about Datça, is a fine beach in front of the town, paired with a natural harbour to its west, also with a beach, called Stony Beach. A third beach is further away, attractively called Sandy Beach.
The town on the other hand is quite dull, most houses are fairly new. The setting here is fine enough, but nothing special to the alternatives in this part of Turkey. But, should you be here and wish for a break, there is a destination just a short minibus ride away: Eski Datça.
Datça has a handful of decent hotels, most seem to be called "pension" or "villa". Hotel Villa Tokur is a nice "boutique" hotel, in the Moderate High range, but sadly enough it is 5-10 minutes walk up from centre. Another alternative is the Villa Carla (If it still is open? Their website is gone), which is in about the same price class.
Eating at Datça is far from bad, there are 3 places competing to be the best in town: Emek, Fevzinin Yeri and the Paptya. They all operate with about similar price level.
Surprise, surprise. There is a nightlife scene in Datça. Not swetty and noisy, but a few friendly music bars at least, plus the nightclub with the rather pedagogical name Sound Dance Club.
Datça is not a small town, so public transportation to and from is good. Marmaris, 1.5 hours away, is served by hourly buses. In summer, the Greek islands of Rhodes and Symi have weekly connections with hydrofoils. Symi is only 15 minutes away, Rhodes 45 minutes. There is also a ferry for Symi, as well as smaller boats doing the stretch a couple of times a week.
Travelling the 40 km out to Knidos cannot be done with public transportation; your options are either a taxi or boat excursions.