Hi Erik,
Using a four layer board is not a feasible option for me as it would cost atleast Rs. 10,000/- [ 225 US $ ] for one board. Obviously that cost is the one time setup cost and for large number of boards the cost would be only 30%-50% more than double sided PTH boards. The nature of my work is not that I can make hundreds of identical boards I only need 4-20 pieces per month for each design.
Because of this reason I will stick to 2 layer boards.

Thanks & Regards,
Prahlad Purohit