I use ice baths 3 times per week. Normally, I try to get in on hard days, about 4 -6 hrs after a hard effort. I don't go in immediately after I run. My protocol is 20 minutes in a waist high bath (I have access to one at my health club) followed by 10 mins in the hot tub. If I don't get in the hot tub, my body temp takes too long to get back to normal ranges. They keep the ice bath at 44-45 degrees. When it's over 55 degrees, I don't get in. The benefit just isn't there when the water is that warm.
It certainly is not the easiest thing to get used to but I think it takes a day off my recovery period. And the first three minutes are the hardest (by far). After that, you're pretty much used to the temp. There are no lasting side effects (contrary to popular opinion that your manhood will never return to normal size).
Bring something to read to keep your mind off the pain.