Here is a screenshot of Half-Life running at 30fps on QEMU in linux.
Sound is perfect at 640×480, but at 800×600 the sound becomes shakey.
Game is very playable!
Instructions for installing:
* download qemu and kqemu
* configure/compile/install qemu
* install windows on qemu
* install half-life on windows
* run half-life
My qemu command line is: qemu -hda hd.img -cdrom ../iso/halflife.iso -soundhw all -loadvm vmsave
where hd.img is a 2GB hardisk image, and loadvm resumes my game from where I left off.
I have also installed MS Office 2003, and am happy to report that Visio 2003 is quite usable.