I've been doing short- to medium-rides (10-20 for daily training, 50-60 on weekends) and working up to touring and the good ol' First Century. I've been using a moderately wide and moderately firm gel saddle. When riding it feels pretty comfy and nothing goes numb, but there's a bit o' chafing and I suspect that, in the long run, it won't go the distance.
I figured it was time to step up and get a racing saddle, a Selle San Marco SKN. I did about 10 miles on it, and for 30 seconds it feels great, then I notice that I'm putting a lot of pressure right on the sit-bones and feel like I'm sitting on a 2x4. I'm sitting a little further back (1/4" - 1/2"), getting a bit wider range of movement, doubt I'm going to go numb or chafe, and I'm not sure, but I might be riding faster as well; but the lack of padding is decidedly unpleasant right now. I'm sitting at about a 45 degree angle, maybe a little less upright.
Finally, the question: Is this something that's going to take a few miles to get used to, and then will be fine? Can the saddle just be tweaked to feel better? Or should I assume that if a racing saddle is uncomfortable after the first 10 miles, I need something else?