Besides expressing the relationship between a part and a whole, recently I found another interesting use of preposition 'of':
Mr Harper's call for a rise in interest rates should not surprise us. When the national economy is growing fast, many economics analysts will claim that interest rates should rise to prevent a situation of boom and bust. Of greater surprise are his optimistic long-term projections for growth in the Australian manufacturing sector.
What is the significance of placing 'of' at the beginning of the sentence? Is it still used as a preposition in the sentence?