QEMU is great, but one specific problem has made it unusable
for me so far. The (fast) machine I want to run QEMU on is not
the same as my (slow) machine which is on my desk. That is,
I want to do the usual X "export DISPLAY=someothermachine:0.0"
game.
These machines are connected by an old-fashioned 10 Mbit/sec
network, which you may argue is obsolete, but I would argue
represents reasonably the approximate bandwidth of 802.11b/g
LANs which are common now.
Anyway, QEMU from cvs is unusable like this, at least when
running WinXP or Win2K. The SDL layer (qemu/sdl.c) blasts
huge numbers of pixels across the network in response to even
the simplest graphical operations. Notably, moving the mouse
pointer is appalling, with an update rate of about twice per
second, which is hopeless.