I do a fair number of print projects every year (posters for promotional events, flyers, brochures, that sort of thing) and have always hand-calibrated -- by eye, if you will -- and relied on
ColorSync. That has worked well for me with both glossy and matte screens (in fact I use a combo at my workdesk) but I have not yet bought a machine that uses an LED screen so I can't speak to that.
I have a long history in the print business which helps my "graphic eye," though I don't doubt I could get even better results with a good calibrator (but a good one costs quite a bit of money!). So far, I've had very little trouble from printers.