The next version will include the ability to swap the scroll wheel zoom direction so everyone can use what they're accustomed to
And you guys are right, the image to 3D add-in can flip the image horizontally depending on your axis orientation. As a temporary fix, you can always toggle your origin placement (toggle flip X-axis in the Options dialog for example), and that should generate the STL correctly. You can then swap it back to import it. We'll have a better fix in the future.
And about the file format, PNG's are definitely the easiest to use. JPG's can have different compression settings and sometimes those can cause issues with the translator we are using. You're best bet is to convert everything to PNG first, and while you're at it, make sure the file and image size is reasonable. That being said, I went out on google and tested the converter with 5 random PNG and 5 random JPG images. The conversion worked correctly on every one. So if you guys keep having issues with this (particularly with a PNG image), maybe post the image here so we can dig into it more.
Pro tip: you can play with the Gaussian filter percentage to alter the smoothing of sharp gradients in the image profile