Softproofing in Lightroom 4.

I know softproofing simulates the way an image may look on paper, but how accurate is it? Does anyone here use it and if so, do you further edit images while softproofing to correct for contrast for example? I just got LR4 but am out of paper right now, otherwise would just print and see for myself.

Cheers

Yes I use it on every image I print. I do my printing from photoshop though. I print portfolios for some of the Seattle fashion shooters and this step is key in the whole printing process.