spider,
what are the impacts ? The answer is in your question itself 🙂
you allow higher throughput to users, so there will be more traffic on the interfaces and in the MFS.
monitor abis congestion and ater congestion, monitor Gb congestion, and monitor GPRS indicators that show whether or not 6 PDCH are allocated in the cell during the busy hour (max busy PDCH, at busy hour) probably your TCH’s are preempting all the PDCH. Check your T1 reallocation and the PDCH decrease.