It is possible to increase the transmit (and receive) gain on Triton TTAT and TTAS boards -- this may help you. Tinker with the gain settings on both station and trunk cards...
I've had similar experiences, but no serious trouble since we switched to PRI.
I dunno about the latency issue bpowers describes -- sounds fishy to me. The quality varies? Some days it's okay? Remote users are connecting via Frame, DSL, etc?