A Telerik filter act as "contains" operator (probably 90% of use cases)
should be good to avoid writing everytime filter by hand
When ComboBox popup is closed and the cursor is in the input field, you can use arrow up and down to select next/prev item in the list.
Allow the use the mouse wheel to do that (only when combobox has focus)
Missing scroll event in comboboxes.
We need this to be able to implement paging functionality for big data scrolling.