To me these are all glaring bugs, especially for those who like to use their keyboard instead of their mouse to fill out forms.

1. Mouse scrolling drop downs/comboboxes scrolls the page when it hits the top/bottom.
2. Enter key opens/closes subgrid instead of putting cell into/out of edit mode.
3. Backspace in drop downs causes browser to go back to the previous page.
4. Comboboxes, when filtering, should always "select" the highlighted item when tab is pressed.(the little auto-complete hack/setting doesn't cut it)
5. There is no easy keyboard way to open drop downs and date pickers in the grid.
6. Tabbing to a button cell and hitting Enter does not click the button.