When Fuse works, it works beautifully. It does so much so well, no other Spectrum emulator comes close, I'd say regardless of platform.
However, it is also riddled with bugs. Actually, my current copy has ceased to work. In this respect, too, no other emulator comes close, possibly regardless of platform. The closest thing I can think of is the famously infamous QA of Sinclair companies, where anything and everything could be broken in more ways than you thought feasible.
Fuse can crash when resizing. Fuse can crash for no apparent reason, and quickly at that. What broke my copy was the keyboard response. It could sit and ignore everything I typed for a long time. It could then pick up a single keystroke at random, print the character, and go back to sleep.. Suddenly it began producing an endless stream of some character it fancied, halting only to crash.
Anonymous