I have never been able to use a slide rule successfully, I grew up after full calculator integration was complete. My mother the calculus and trigonometry teacher is a wiz with one though. (she is a nerds nerd, who else will sit down and do formulas because its "fun")
Most of my work is performed on a TI-84 (mainly sin, cos, tan functions) or a construction master V. The construction master was carried in my pocket everyday for the last 10 years, it is invaluable in my construction life.