The Sungem device did not get merged into 2.8, at least using -net nic,model=sungem. Nor did the VGA changes. Not sure about the RTL support though, but it doesn't seem like it got in either
Mouse control seems to be worse in 2.8 when starting out windowed, with the host mouse being visible when full screen and the guest mouse moving too slow compared to the host mouse. SDL does not work in Stefan's build for 2.8, by default. I can confirm that using -full-screen accentuates this problem, by merely zooming in rather than scaling when you boot up with this option (which is a problem for non-4x3 resolutions).
The version of OpenBIOS included in 2.8 is a version from November 24, 2016. Looking at the QEMU mailing list, the last post I see about PPC Mac emulation is from October 1.
As for MacBench 5... Performance also seems to have slowed down from 2.8pre, with a score of 135 for the floating point and (somehow) 42
for the processor vs. a Power Mac G3/300.
Shutting down also doesn't seem to work right when done through QEMU rather than doing it within the OS.
I'm using Stefan's 64-bit Windows build of QEMU 2.8, compiled on December 21, 2016.