A search for XDM would return many threads hashing this subject out.
I own an XD-40 subcompact and an XDM-40 bi-tone.
Here are most, if not all, of the differences between an XDM an an original XD: 3 interchangeable backstraps, higher magazine capacity (without widening the grip), slightly different ergonomics (tapered slide, wider sharper notches where your fingers grip the slide to rack it, lots more checkering or stipling on the grip), match grade barrel, slightly crisper trigger with a shorter reset (it feels awesome) slight serrations on the rear sight to help reduce glare, no trigger pull necessary to disassemble, and a slightly higher price tag. But I really like mine, it's extremely accurate, and as with all XD models, points naturally and feels great in the hand. The grip angle and width, dimensions, etc. honestly feel almost as good as a government 1911. I'm still under the 1,000 round count on mine, but I like it more and more each time I shoot it.
True, it has been hyped like crazy. But just because something gets a full spread in all the major gun rags and is hyped like crazy all over the internet doesn't mean it's just hot air. It does offer some slight but significant improvements over the standard XD and is a fine firearm.
