I had the old rack version of this from way back in the day. I decided to check out the new foot pedal (sonic Stomp) version on my MKIV. I've had it for a couple of weeks and really like it. it really works well on R1 and 2 to add some nice clarity to the sounds. It's a subtle sounding pedal unless you crack it all the way up. If you do turn it up to far it can start to sound bad. It sounds great straight into the front of the amp and also sounds great in the efexs loop. I think it's a great tool to use with the MKIV. It adds a little sparkle to the cleans and gets rid of the mud on R2. It's not as fun as buying a overdrive or delay etc. pedal, but it really helps me dial in my mkiv. $99 wish it was $50 but still worth it IMHO.