I think I must be a tasteless heathen, or maybe just really lazy but I've literally never calculated IBU's for any beer I've brewed. After kinda sorta wandering off the path of the recipes I borrowed for the half dozen or so batches I approached hopping in a similar way to the way I cook, see what the AA% of what I have on hand is and wing it on bittering. With flavoring, aroma and dry hops I'm much less scientific, if my experience with, or the description of the hop more or less sounds like it's appropriate I'll probably use it. Honestly, my ability to discern the difference between a beer brewed with one hop and another identical beer brewed with another hop is very limited - I suspect that in blind taste testing 75% or more of the population would be no more accurate than I am.
As far as bittering hops, 5 years ago my preference was the more the merrier, today I prefer a MUCH less bittering and maximum aroma. Funny how our tastes change, I used to love Voodoo Ranger DIPA, but now I have a 4 bottles of a 6'er in the fridge that've been there for months waiting for some else to stop by and drink them, I can't hardly gag 'em down anymore. Nasty, stinky sock-feet beer!