Having laser on my chest currently.
HT greatly reduced thickness and growth of my chest hair but hasn't eliminated it, I got annoyed and chest shaving every couple days to wear a top such as shown in my profile.
Getting four treatments for the chest location concurrent with the armpits(covers down to a row of laser across my sternum, $200 per session charge.
I have 18 months of robust HT. As for hair changes, the most profound has been the complete shedding of my back hair, something I though would need treatment... My legs have shed 60% and I expect another 20% will go over the next few years, the entire male secondary inner thigh pattern thankfully shed. There has been a body-wide change in the thickness and growth of hair that didn't shed to pretty much female norms. Obviously with the remaining thickness and quantity of my chest hair, I felt treatment is appropriate, after laser session 4 I'll be plenty willing to shell out a few bucks for electrolysis, of remaining hair on my chest, armpits, the annoying ingrown ones on the back of my legs, etc.
edit added: You asked about, pain? yes.