I could see using SSD for log files rather than data storage. I would have also increased the RAM in the systems since SQL is RAM intensive. The combination should give the best performance as well as reducing the total cost.

Most of the performance issues I have found are related to poor file distribution, log and data on same drive etc. While data writes don't suffer as much, the TLOG operations do and that really has a negative effect on the performance. Using a fast access drive for TLOGs should really help with the overall performance.