I won't comment on time accuracy since that's like estimating how long a marathon takes.
As far as accuracy goes, I wouldn't take their elevation profiles too seriously since it seems to significantly under estimate total ascending and descending elevations. The net elevation change might be accurate but the rides are usually tougher than the elevation profile indicates.
I used to take the url of the ride and convert it to a GPX using
www.gpsvisualizer.com. Both google earth and Delorme Topo showed significantly more ascending elevation than google maps did. You can no longer use gpxvisualizer to do this without jumping through some hoops, but mapstogpx.com seems to work. Gpxvisualizer uses the Digital Elevation Model (DEM) which I believe is what google uses so I'm comparing the same basic data.