I also have the TS3, bought it on sale after the TS4 came out and I really love it. When I'm not around dirt and sand I shoot with professional gear, and I'm happy that they introduced the manual setting in the TS4 so you can expose pictures how you want. The Leica lens is not bad, but it's also only 5x zoom, and can get scratched as it's always exposed.
I love the GPS on these cameras, if you load them into a program that enables geo-tagging you can see where you caught each of your fish. The HD video is good too, I find it works well for underwater release vids.
As with any underwater camera, just make sure the seal for the memory card and battery docks are free of debris and are well maintained. I had an olympus underwater camera before this one and the seal degraded and let water in, which killed the camera. It also had a retractable lens cover that stopped working once it got dirt in it, so watch out for that.
I don't usually touch up photos afterwards, so here's some examples straight through the lens.