Every picture is differrent and grays seem to be the hardest. The software allows a lot of adjustment so you have to play with it a little. As far as contrast and color issues, just make sure you cover the full light range in the shot and it usually isnt too much of a problem. It's hard to get black lines like powerlines or rope on sails to not cause distortion against a bright solid background like an overcast sky though. I like to have more overexposed images than under exposed images in my HDR images as it reduces the noise issues in the mid-tones, so maybe -3 EV to +5 EV on your bracketing. It depends on what you are trying to do, but the program makes it pretty easy to try different things, doesn't take hours of time and is much faster and easier than using a program like Photoshop to adjust your curves manually, though you can get some crazy results with that method. Here is the train image with the color blown out and a steep exposure curve in Photoshop using manual HDR, I wanted the train only visible in the shadows so it would be ghostly.