Has anyone had any luck with these?

I finally installed mine and while it works, it just doesn't have the sensitivity or the smooth rolling of the OEM trackball and I can't pinpoint the reason for that...

Do these things break in over time and start to function better?

I really like the look of the new trackball but if it doesn't start to perform better I may very well switch back to the OEM trackball.

It will get smoother of time as it gets dirty (ewww). If you have an older model they actually had less course surfaces than the new ones. Actually, I'm wondering if something is up as the rough one should be more responsive.

E-

Agreed. You just don't notice it wearing out. After a month or so it will feel normal.