I'm a huge fan of the Habit - they started in Goleta/Santa Barbara and when I worked down there there were only two locations, now they're popping up all over. I was really glad when they opened up the one in Roseville. IMO, The Habit is equal (if not slightly better) then in-n-out.
I really like Habit too. Wish it was just a bit closer.
http://habitburger.com/Gatsby's Diner is a newish place that has great burgers in Sac too.
2598 Alta Arden Expy
Sacramento, CA 95825
(916) 977-0102
Very 'gourmet' and it's in what looks like an old teppanyaki place, so the chef grills everything out in the middle of the seating area, instead of in the back. Makes for a nice little show/distraction/gimmick.