It depends on what you are trying to do. Softice was good for "kernel" debugging, rather than just simple user space programs for which things like turbo debugger (and more modern solutions), were as good if not better.
For windows kernel debugging, there is windbg, kd, and assorted "emulation" methods like qemu's gdb stub. Similarly for linux/kgdb/etc... OTOH, Softice had a number of OS data structure aware commands in the late 1990's which are only really available in something like windbg. In theory you could write kgdb macro's to perform most of that functionality for linux/etc but it doesn't work out of the box.
Although in the end, the logical replacement for softIce, is a JTAG debugger of some form. A fair number of the ARM platforms work with DS5/Dstream which provides source level debugging with far more functionality (for example trace level timing information) than softice as an "ICE' ever did. I guess its the same for intel's ITP-XDP3/system studio products these days.
Again, it depends on what your trying to debug. AKA do you need the "ICE' (aka JTAG these days) functionality, or are you just looking for a powerful kernel or user-space debugger.
