I forgot that Quake 2 had the option to use a software renderer. It looks amazingly good. It is hard to compare to my memory because back when it was new there were no CPU's powerful enough to run it at high resolutions in software mode and have any sort of playable framerate. Seeing it at 1024x768 in software looks great. It doesn't have colored lighting (like in OpenGL mode) but I bet that isn't a technical limitation but a choice made to make the software renderer run faster. It is not nearly as moody as Quake 1 is but it looks good.
I would love to see what a modern CPU is capable of doing for a software rendered game engine built to use its capabilities. I cannot put my finger on it but there is just something about a game rendered in software that I prefer. I remember the first time I saw Tombraider and Quake running on a Voodoo 1 video card and my jaw dropped, but back then you had to have 3D acceleration to get higher resolutions and acceptable frame rates. The true benefit I can see for a modern Software rendered engine would be that it wouldn't have to be 'stuck' to any particular API. Just my incoherent ramblings.
Gateway 2000 Case and 200-Watt PSU
Intel SE440BX-2 Motherboard
Intel Pentium III 450 CPU
Micron 384MB SDRAM (3x128)
Compaq Voodoo3 3500 TV Graphics Card
Turtle Beach Santa Cruz Sound Card
Western Digital 7200-RPM, 8MB-Cache, 160GB Hard Drive
Windows 98 SE