If you are using earbuds, there are separate versions of each environment that have been balanced and equalized for the different characteristics those headphones have.
The nicest addition in this new version is that multitasking is now supported. You can leave the app and the sounds will continue to play. Of course, you should be relaxing and not fiddling with your phone, but the feature is still a good one. The latest version also has reduced CPU usage so your iPhone battery gets a break.
Users who really get hooked on this app may want more environments and you can do that with in-app purchasing. Additional natural sounds cost between US $0.99 and $1.99.
Of the free sound environments, I like Infinite Shoreline the best. It takes you to the beach, with waves moving from right to left as they gently come to shore. Of the paid environments, I really like Helios Falling, recorded at sunset with a symphony of crickets, an Owl, some brief rain showers and a nice breeze. One suggestion if you try the app. There is a temptation to play these sound loops too loud. Get the volume down to more closely approximate the way nature sounds, and I guarantee that your experience will be better.
There is a sleep timer, which is handy, and when sleep time is reached the sounds fade out. Although headphones are really the best way to experience this app, it certainly works over speakers. I'd like to see a wake-up function built into the app, because it's a nice way to start the day.
Naturespace also works on the iPad, although an iPad specific version doesn't exist yet. The audio is the same, but the app looks a bit small on the iPad screen. The developer advises retina display support and a universal iPad/iPhone app are in the works.
There are other apps that play loops of recorded sounds, but I think the Naturespace sounds have superior recording technology and quality. You can almost reach out and touch the birds and feel the wind on your face.
Naturespace is a great relaxation tool after a long day, on an airplane flight, or anywhere you'd like to get a respite from the cold hard world. At a cost of 'free' it's a no-brainer, and Naturespace may really improve and enhance your relaxation time.