I use my 500HD purely for effects and control.
I midi out to my JVM410C and have set up identical patches to simulate the 12 channels on the amp, I use the expression pedal to morph into solos. Heel down gives me my amp only, toe down brings in whatever else I have switched on including boost, I do this by putting a pan effect right where the chain splits, and put my front effects to one side, 4 cable method through the amp, time based effects and clean boost after the fx loop controling the delay mix with the pedal as well.
This also means I can switch off the boost, go toe down and bring in any effects on my rhythm setting as well. So versatile, go from clean amp to full on distortion and delay smoothly, then back off leaving the delay trails going, awesome.
Amazing piece of kit, my only gripe is why can I not access more effects as i'm not using any amp or cab modelling, surely there is enough processing power, amps should class as effects with regards to processor useage.
There, I said it.