In addition to Salamander Grand Piano I've converted some of my files to sfz. Musescore seems to handle it fine (better than SF2 actually) when it comes to playing the SFZ instruments but:
- deleting an instrument, while removing it from the Synthesizer's Zerberus list, doesn't actually remove it, so you can still select in the mixer.
- adding a new SFZ doesn't refresh the Mixer's instrument list so you'd have to close/reopen it to see the new additions.
This are minor bugs that can be worked around, but thought I'd note it, in case they're easy fixes.