phone history threading
having come from iPhone and loving my WP7.5 device, i miss the threading of calls. example you call Mr. Smith 6 times and he calls you twice, have them collapsed into a list that you can expand, this reduces the size of the list and lets your be more organized. searching by missed, Called, and all would be great at well.
Jonas Stawski commented
I think the call history screen is one of the weakest points in WP7. I don't know why the summarized call history of WM6.x was not added to WP7.
What a great idea!