I try lifing hard without them, but for real maxes I need them:
Deadlift:
No straps: 485lb
Straps:.....550lb
Rack dead:
No straps: 485lb
Straps:.....600lb+
Chins
No straps: 20ish
Straps.......18 with 45lb plate!
Bent rows:
N0 straps: 245 x 8
Straps:.....295 x 7
All beltless, but you get the picture!