According to a TfL press release, "early results from both pilot routes suggest an overall increase of 25 per cent in cycle journeys".
However, these counts were taken in August, when the routes were attracting quite a lot of media interest. This attracted cyclists keen to see what the CSHs were like. I know because I was one of them.
The press release didn't give much detail beyond the headline figure of '25% increase'. It will be interesting to see:
a) if the increase is sustained year-round;
b) if the increase was a result of displacement from other routes (i.e. existing cyclists diverting from other routes rather than new cyclists);
c) if the increase only applies on the CSH route or if there has been a similar increase on other routes.