What do you mean by smooth? It doesn't seem like you were using a high dpi mouse before, so I'm inclined to agree with other posters that yours has a defect, rather than that you're just experiencing its relatively lower tracking ability, which should be perfect smooth and acceptable depending on what you're used to. I certainly would not consider the MM to be a high end mouse, but rather a specialized one whose main offering is multitouch, though at the expensive of ergonomics and performance.
Is the multitouch important to you? If it is, then obviously, keep the mouse and get a replacement, but if not, consider getting a gaming mouse. I'm not a big gamer and don't play much (or really at all anymore), but the improved tracking makes a huge difference just in everyday use. I recommend it for everyone regardless of whether they game or not.
Edit: On second thought, do you have a strong BT connection? It could be an issue of it dropping out sporadically.