When filmed from the boat the skier appears quite a way away on playback depending on line length of course. It usually suffices however because of the high quality picture so you can simply move your head closer to the screen to see what your doing if that makes sense!
When it is attached to the skier it gives an awesome video but I'm not sure how good it would be for training because rather than showing you and your movements it shows the tip of your ski and the buoys coming at you. This is where the iPad comes in because someone sitting in the boat can see what the camera is seeing in "real time" (about 5 seconds behind at best). I had problems with the wifi (how the video is transferred to the iPad) - it kept disconnecting which is frustrating.
You can also attach it to the front of the ski facing up at you which would be more productive for training with I'd say. You can see all your movements - where your hips are, where you are looking, knee bend etc...
When I brought my camera I was under the idea that through the inbuilt wifi you could transfer the GoPro files onto an iPad or iPhone for playback so you can slowmo and pause it etc. It can't do this however - all you can do is watch it live which is pretty useless IMO. The only way to play it back therefore is connect it to a computer and then play it through that. In 1440hd however most computers will lag because its just too much for them to handle.
If you do want to watch it through an iPad you need to download a movie player app because the stock iPad movie player does not support the kind of files the GoPro produces. You need to transfer it onto the iPad through a computer because the USB adapter cords that apple makes (so you can plug a camera straight into an iPad) packs a fit when you connect a GoPro.
All in all I didn't think the Hero 3 lived up to all the hype. GoPro missed a heap of seemingly obvious problems for example when you get it to use it you need to download NEW SOFTWARE for it just so that it works. That should be done before it leaves the factory door IMO.
The brilliant image it produces almost makes up for all this however.