I knit pretty much all my hats from the bottom up. Why? Because I don't find the bound-off edge stretchy enough for the bottom of a hat. I also don't like to knit "soul-crushers" (my term for any knit where the rows/rounds acquire more stitches as you get farther along), with the exception of the OSW which does not bother me for some reason.
Many people don't like knitting hats from the bottom up, however, because of the dreaded "hat hole" (pictured above). You don't have to get hat hole! The following technique occured to me when I made my very first hat, and I'm really surprised I haven't seen it anywhere else. Once you've drawn your yarn tail through the remaining stitches and pulled tight, drop the needle down the central hole so the tail is on the inside of the hat. Now look closely at the hole. There's the hole, then a round of relatively loose stitches around it, followed by a round of "normal" stitches. Poke the needle up through one of the normal stitches, just beyond the edge of the looser stitches. Bring the needle down again, diametrically opposite of where you poked it up. You have just made a line across the hole. Pull the yarn tight. Now make another line across the hole, the same as the first one but perpendicular to it. Pull tight again. You've made a plus sign covering the hole, which is now virtually invisible. The yarn tail is on the inside of the hat. Turn the hat inside out and weave in the tail. Ta da!