I think it would be better to implement this as a new series type! I am not sure if it is general enough for the core library, but it would be an interesting example in the example library!

Good idea! I have added issue #343!

Yes, I think this would be a good idea! Then the project/assembly name should be OxyPlot.Eto!
I have added issue #341

This looks like a bug, can you add it on GitHub?
When an axis is not visible, it should not be possible to pan or zoom.

I think this custom tracker would be a great example! Anyone up for it?
This feature could also be covered by Issue #49

For WPF/SL (and maybe Win8, I don't remember) it should be possible to define a custom trackers that shows a value for each series. The default tracker does not support multiple values - remember the LineSeries does not require monotone increasing x-values and could have many intersections for a given x.

Please add a new feature or example request in the issues at GitHub!

The IRenderContext does not support transforms or rotated ellipses. This feature can be added, but must be implemented on all the platforms....
A work-around is to render the rotated ellipse as a polygon by calculating the rotated outline. This will work on all platforms with no extra work :-)

Please add the new feature request to the issues at GitHub!

This looks like a bug. Please add it to the issues at GitHub!

Did you see the examples showing a heat map on polar axes? Performance is an issue, but it can be done!
Implement as a "series" if it should be "trackable" (mouse click to show value) otherwise "annotation".

The hit testing is currently only checking the arrow. It should be very easy to extend it to test the text. You can add this as an enhancement in the GitHub issues!