e.g. in the demo data set, query avg(depdelay) and group by dest_lat/lon and then show on the map?
Currently the pointmap displays non-grouped data only, so you would only see depdelay for the topmost point for the lat/lon, which is chosen non-deterministically. We have work under way which will allow for this map to represent aggregate data as well-- will post here once it has landed.
Within the current non-grouped setup you would set Lat and Lon as measure, and choose depdelay as either your color or size measure.