Yes sir, actually more like 12,000 rounds now, I had a busy weekend.
I received my parts from S&W and decided I needed to wring it out after detail stripping and repairs were made.
I had 500 rounds of +P+ 115gr. Gold Dots, 1000 rounds of CCI Blazer, and a few boxes of Winchester "white box".
It ate the Blazer without a hiccup, but I kept getting early slide locks with the +P+ stuff, I finally realized that the additional recoil and my high thumbs grip caused my thumb to bump the slide stop lever, locking the slide back early.
An hour with the Dremel, file, and cold-blue, and I was back to the range. (I'm a perfectionist, had to make it look just right). I fired the rest of the +P+ and the Winchester with zero problems.
All is good in P99 land again.
Funny! I did the exact same thing to my P99 about 4 weeks ago. The occasional failure to lock the slide back on an empty mad was causing me to lose confidence. Best mod I've made to the gun yet, save the night sights. Initially I squared it off just like yours but had a lock failure in rapid fire so I diagonally cut it from the portion that intercepts the slide at a 45 degree angle forward. It actually looks pretty cool. I doubt I spent as much time as you did honing the edges to perfection but it still looks good. Haven't shot it with the latest change though. Personally I think oversized slide releases are a liability and encourage poor manual of arms. Not much reason to have the long tab there except to accomodate different hand sizes.
I'm glad I'm not the only one psycho enough to deface my P99 in search of the perfect fighting tool - besides, it adds character.