Earlier in my career I wrote ROM monitors for the Motorola 6809 and later the HC11. We used the ROM monitor method because the organization could not afford enough ICE's for all of the developer seats. It was a great monitor (if I do say so myself) and did it's job well, but it also required a Logic Analyzer with disassembly to match the equivalent power of a good ICE.

My last two ICE's were about $500 a pop (Acqura) and they are both brilliant. Since they are bondout versions of the target CPU they are functionally IDENTICAL to the final device. I've never had any issues when removing the ICE and going with the actual silicon.

Before that we acquired (and I still use) a Cypress ICE. Though not as nice as the Acqura's, it has very few (well documented) differences from the real chip.

I wouldn't go back to a ROM monitor if you begged me.

GB