I've just returned from Krabi and my experience staying in Aonang was not what I had envisioned for the perfect Thai beach/island vacation. There were more shops & restaurants as others have said but I was hoping to escape the commercialism. Also I was quite disappointed that there wasn't much happening around the beach - there were a few bars and restaurants but there seemed to be more of a family vibe. Worth noting that I was there in low season so maybe it's a livelier scene in high season. From what I saw, Aonang seemed to be more of a base for people to take daily speed boat tours to explore the islands and for those with an interest in the mainland, rather than a destination to enjoy entirely on its own.
*For a second opinion, I suggest you find a copy of the Thailand Lonely Planet (not the Islands & Beaches book) and read what it has to say about Aonang.
Our last night we finally discovered what we had been looking for on Railay just 15 minutes away. It's a part of the peninsula completely cut off from the mainland by the limestone rock formations so only reachable by longtail boat. From the research we did, we thought that Railay was just a beach to visit in the daytime, we didn't realize that there was a backpacker hangout with the range of accommodation (rooms, bungalows, resorts), beach bars and chilled out vibe that we were looking for on the east side. On the west side there are also quieter restaurants, resorts, and a beach. It is a small, albeit stunningly beautiful, place so not sure how much time you can devote without getting bored. I could have easily spent the whole four days we had. I would have enjoyed at least two days on the beach & wandering around the non-motorized paths, rock climbing for a day, and maybe one of the speed boat tours to the other islands (you can arrange all the same ones that leave from Aonang, including the ferry to Ko Phi Phi). If I had longer I would have spent a few nights on Ko Lanta or Ko Phi Phi. We only visited the latter in the daytime but we could see there was more of a party scene there - not my preference, but the island looked big enough that it would be possible to find peace & quiet if that is also what you're after.
One disadvantage to Railay is that you have to wade into the water, sometimes waist deep, to get into the longtail boats so difficult for the elderly or injured. Also the boats can't run after a certain hour at night.
Of course plenty of people enjoy Aonang and what’s on offer, but for me Railay was what I sought. I thought the research I had done before the trip was adequate but since things didn’t end as perfectly as I pictured, I wanted to share my experience to provide those making plans with another perspective. If you are 20/30 something, backpacker looking to mix with other travelers and relax on one of the world's most beautiful beaches after a crazy few weeks traveling around SE Asia then I highly recommend your consider Railay as your destination. To me it was paradise.