I have always had a good experience with:
Havoc
Lifeline
Deathwish
Midheaven
Relapse
Bridge 9
Interpunk (expensive but I always get my merch in good condition)
Fat
Kingsroad (expensive as well and a little slow but no real issues)
Southern Lord (slow and a little disorganized but they were communicative and rectified all issues) - I will probably go through their Blue Collar distro in the future.
I think I have been spoiled by the evolution of mail order. When I first started buying records I would stash money in an envelope, send it to an address I found in a zine and hope for the best. Now I get stuff from people like Deathwish within days of ordering.