In reply to Swig: Matrix is plenty busy, have a feeling that the number of people regulary visting a wall in Sheffield must be going up, I rotate round the Works, Foundry, Matrix and Edge, for bouldering, and other than the Edge, which is obviously mainly for roped climbing, the walls are uniformly busy to rammed most weekday evenings and weekends.
Only shame is the walls don't club together for a super season ticket that is valid across all of them!