The C7: Bested by a P166
Anectdotal evidence of why the Via C7 is an inadequate processor:
Back when I was first using Linux (around 2001), one of the things I really got into was squeezing as much performance as I could out of my old, second hand desktop. At the time, I was running with a Pentium 166 MMX. Playing MP3's actually took quite a bit of CPU power. It was worth my time to learn how to apply a patch to XMMS (a Winamp clone) which enabled MMX decoding of MP3's. With the patch, playing an MP3 would drop from 30-40% of the CPU to 1-2% - an amazing improvement.
So, on my old Pentium 166, I could easily play MP3's and do something else at the same time. Even before the MMX patch, I could play MP3's, just with the rest of the system running slower. It was actually one of the reasons why I used Linux as my primary OS.
When testing, the HP MiniNote lagged playing an MP3 over the network using the mplayer command line program while installing KDE 3 with apt. If that isn't damning against Via's CPU division, I don't know what is.