I ran my 8th Boston yesterday and agree with the previous poster who said that the conditions were good, but definitely not perfect. The temperature was pretty nice, though I would have preferred it a little cooler. Standing at the start, with the sun on us, I thought, "This is not as cool as we thought it would be.' The wind was a significant factor and often I noticed people were not running tangents. As soon as I would veer out of the pack to make a more direct route I would be reminded as to why no one else was doing it either. The headwind was making a difference and it felt easier to draft. As is common for Boston, the wind picked up as we approached town and therefore, the sea. It was pretty rough over some stretches.
That said, I have seen much worse headwinds and much higher temps there, so all and all, a pretty nice day to run Boston, but not a day for course records.