By default, WAAS applies full optimization (TFO+DRE+LZ) to MS SQL traffic. There is currently no SQL-specific application acceleration. The performance benefit you can expect depends on the nature of the transactions (i.e. the volume of data) and the WAN characteristics (bandwidth and RTT latency).
Practiacally speaking, it's likely that you will see a decent reduction in bandwidth consumption, but less improvement in overall user response time.
Regards,
Zach