Hey Morten,
Thanks a lot for that reply.. The ExtentChanging works... and you are right the user does not need all 50,000 points, BUT, what they do need is an accurate count of points that are contained in the cluster, and this is not possible without downloading all the points, right? If it is not downloaded, then it is not counted in the cluster...
And the initial extent of the map will cover the area of all 50,000 points, and the users would like to see this cluster at this extent.
But as far as the features go, they do not need to see them until zoomed way in, and "OnDemand" is perfect for this. Also, the "on demand map tip" you showed off will be great too. I was actually at this DevSummit session and that plus several user requests have inspired us to move from a dynamic service layer to a feature layer with map tips and clustering :).
This data really fits the clustering concept well, would be nice if the cluster could be generated server side.
Thanks a lot for the help! And that great DevSummit session�?� please let me know if you have any more ideas.