I've had one for a month or so. Overall, I have to say I'm not especially impressed with it.
There's a fair amount of lateral play in the blade, both opened and closed. Seems to me the scale material around the pivot just isn't well-supported enough to keep things tight. I tried tightening up everything I could, but the problem persists. It's not that I'm worried about faliure, the lock-up is tight, there's just a lot of lateral slop at the pivot.
The edge grinds were very uneven, both along a side and between sides. I spent a lot of time with the diamond stones getting them evened out and symmetrical. That said, once I got them straightened out the 440C did take, and does hold, a good edge.
There's really no "spring" in the clip, it's very short and very stout. So while it does hold onto the pocket very well, it does not unclip or clip onto the pocket smoothly. You can pull up on it to loosen it up, but be careful you don't bend too much, because then it'll just be loose (no spring).
Blade is thick, especially for such a small knife, so it doesn't slice as well as it could. Another problem with slicing ability if the V-hole. It's large, especially relative to the blade lenghth. I've found that sometimes when I'm making long cuts that the material being cut gets hung up on the inside of the top of the V-hole.
Doesn't open very smoothly either.
For the money, I think the Spyderco Cricket is a much better put together package; better slicer, smooth action, better clip, no blade play.
But of course that's just my opinion. I'd be interested to hear from others with experience with the Mouse.