Just posted in greater detail over at the Marshall Forums, but first impressions are very positive after dropping this into my Marshall DSL40C. It's a subtle shift in tone, but it helps roll off the harsh highs, bumps up the mids, and tightens the lows. At least at lower volumes, the cleans can get sweeter, and the distortion can get gnarlier, with more control over the presence and the mid-range response. Can't wait to get it really pushing some air. Not bad for 80 bucks with free overnight shipping!