And I've just found my first bug in the chart control...
Only a minor one.
If I plot a graph then this is how it looks on the web UI:
However, if I plot the chart and then call SaveImage before displaying it, then I get this:
For record, the saved chart looks fine:
In my case there's an easy workaround - but thought someone might find this interesting...
Edit - I've also just tried calling SaveImage twice in a row - I see the same effect - in the second chart the data is corrupted.
Workaround/fix from Alex Gorev on the Msoft forum - if I set the series XValueType then this prevents the problem :)
series.XValueType = ChartValueType.DateTime;