The slide stop should have a smooth face, so it's normal. Also, the detent does not have that much spring pressure. More than likely it's your mags, or you MIGHT have a tight fiitng slide stop where it contacts the link and bottom barrel lugs. I kind of doubt that though.
Put an empty mag in the gun and pull the slide back. When it catches, look to see if the lock of the slide stop goes all the way up, or just partially. It's fairly common for factory Colt mags to only puch the slide stop up partically after the last round. You might have weak mag srpings, or maybe just followers that are not properly shaped, or even a slide stop with a lug that is undersized.
There are other things that might cause it, such as a burr caused in the slide stop notch on the slide from improper re-assembly. Also, like I mentioned, the slide stop might fit very tightly in either the frame or be rubbing due to excessively tight fit of the link/lugs. Youcould theoreticlly have an oversprung gun too, but you would probably see some FTE problems as well.
Here are a few questions. What mags are you using? Are they the same age as the gun? Is the gun relatively clean? Is the slide stop original? Is the recoil spring original or is it heavier?