Temps in the mid 70's, direct sunlight, and a bit of a tail wind. I wore my heart rate monitor because I doubted my ability to judge my effort without it. I don't think I did a single training run in temps warmer than 55 degrees. Monitoring my heart rate periodically seemed to really help me. I'm totally thrilled with the outcome, especially on a warm day. My halfway split was 1:24:57. I ran pretty even pace and finished with a slightly faster second half.
It was a blast to see so many friends along the course. I don't feel like I could have gone any faster. The sun took everything out of me. I took liquids at every mile except for mile 25. After finishing I got an awesome massage and walked home along the Charles River. It was a beautiful day for spectating. I can go up and down stairs just fine and actually feel pretty good. No injuries or joint soreness, just some sore muscles.
I did well with nutrition before the race, eating pancakes, bagels, a cliff bar, banana, etc. I must have had 2K calories before the gun went off.
Boston is a great race!