I don't work for any photography related company, so, I'm not trying to sell you APS. Here you will find my comments based on my experience by shooting APS.
One of the things you will find about APS is that there are no professional APS Cameras in the market, nor APS professional film. All you can find are point-and-shoot cameras, and some SRL models. All pictures in this site have been taken with a Nikon Pronea 600i which was the fisrt APS SRL Camera from Nikon. APS cameras are smaller and lighter than 35mm cameras, and the film is more expensive to buy and to develop. Here are more comments:
1 - 3 Pictures Format: This is an excellent feature. This expands your creativity, point of view, and enjoyment of photography. You can have a better perspective of real dimension with the panoramic format, or capture just what you need with the other formats. The viewfinder in your camera is set up for the Horizontal format. The print of this format is a little bit larger than the traditional 35mm. Once you get used to this format, you don't want to use the Classic format anymore. Another good point is that the viewfinder of most APS cameras is divided into section to delineate the formats. You have have two horizontal and two vertical lines. This is an excellent tool for composing in general. You can align objects to these lines, improving your composition (this is called the rule of thirds in photography). At the same time, it takes some practice to get real good panoramic pictures. Something that is not so good is that the APS negative is smaller than the 35mm. This mean that you can't enlarge a picture as you can with 35mm. Now, let's be realistic, how many picture have you enlarge during the past 12 months?
2 - Mid Roll Advanced: This is excellent, a definitely advance over 35mm cameras. Now, don't interchange films and cameras. If you begin shooting a film with one camera, finish the roll with the same camera. At the end of the day... how many cameras do you carry on?
3 - Print Proof: This feature is good. It helps you keep organized your negatives.
4 - Negative Stored in the Cartrige: I think this is good to protect your negatives, and to keep them organized, along with the Print Proof, but if you take a lot of pictures you will end up having a lot of useless plastic pieces. It is space comsuming.
5 - Smart Film: This is an advantage mainly if you have and APS SLR camera. Point-and-shoot caremas primarly have only one aperture size and, in some cases, different shooter speeds.