YAPE is a decent no-nonsense plus/4 emulator. It has been developed for 10 years by now and it is available in Windows as well as multiplatform editions, although some of the latter lag several versions behind the former.
Here're release notes for 1.0.2:
A badly needed update: some nasty bugs have been patched as well as the in-memory bitmap of the printer emulation is made visible via a GUI window (only as #4 for now because me being lazy). Anyway, let's see what's new this time:
+ printer job window (for now #4 only)
+ turn off variable length buffering properly when recording media (fixes occasional clicks)
+ not scanning joysticks when unavailable (Message Queue driver slowdown)
+ column width and line feed bug for MPS803 emulation fixed
+ regression bug in the printer cycle counter ironed out
+ awkward TED drawing bug patched
Visit official homepage for further information and latest version of emulator.