I have a Crimson Trace on my Sig P2022, I had some issues early on but CT are great for customer service and sorted everything out for me, now it works great
Crimson Trace makes a great (albeit overpriced) product, with fantastic customer service. I've heard a few complaints about Lasermax in the past, but they weren't widespread.
Doesn't affect anything. You can still lock it manually, and it still locks when last shot fired. A few guys didnt know they had it there until I told them how to turn it on. I love mine.