How much do the mascons on the moon affect surface gravity?
Upon some google-ing and wiki-ing I found this image of a gravity map of the moon:



That scale up the top is measured in milli-Gal which is thousandths of a cm/s^2. For scale gravity is ~9.81m/s^2 which equals ~981000mGal. The difference between gravity at sea level and the top of mount everest is 2Gal, or 2000mGal, which is 0.2% of average gravity. On the moon, the variation seems to be about 1000mGal, with the average being 162000mGal, which is about 0.6% of average gravity.

In conclusion, on the surface, there is no noticeable difference. Not to a human anyway.