I recently bought the
Steel Series Xai to replace my old Microsoft Intellimouse that was malfunctioning. I struggled for a long time to find a mouse that I felt could compete with the Intellimouse, but I've been very happy with the Xai.
Yes, it's very expensive (90$). I'm not sure yet if it's worth the money, I think that will depend on how durable it is and how long it lasts. But I really love the feel, even more so than my old mouse. The tracking is great (it's a "gaming" mouse after all, with a high dpi) and its special feature (and I guess the reason it costs so much) is that you change all your settings (like sensitivity, speed, etc) on the mouse itself, so you don't have to rely on Windows to interpret/adjust your mouse input. I guess that's supposed to provide some sort of advantage for gaming, but it might just be BS.
But anyway, I still really like it. I've finally found a mouse with the shape and layout that I'm used to. It's very comfortable. And it's also lightweight. When searching for a new mouse, I realized I'm what they call a "claw gripper." I hold my mouse with my thumb and pinky while the rest of my hand hovers above it. Instead of moving my whole hand, I just flick the mouse around with those two fingers. The Xai is perfect for this style.
It's probably not what you're looking for, but I decided to post this on the off chance that you (or someone else reading this) has similar problems with most modern mice. I was looking for a modern replacement for my Intellimouse for years.