I have used MS windbg. I didn't use SoftICE because it has some problems
with my mouse and freezes easily. I only used windbg for user mode app
debugging, not kd or kernel/driver debugging.

One good thing is that windbg can handle large size executables, like 50MB.
Its short cut keys are also the same as VisualStudio (a convenience for me).
It has all the basic stuff and interface is OK. Not so great but suits my need.