The SiS315 performs roughly between the GF2 MX200 and MX400 in terms of performance.
It has excellent 2D visual quality, and DVD playback however. Having 128MB of RAM on an SiS315 is an absolute waste however and is really there only for marketing purposes. The card has no where near enough power to play at resolutions at which you might see any even remote benefit to having 129MB.
The SiS315 is an excellent budget card, and quite versatile. I would have no problem recommending it for someone that isnt going to be playing many games, but it's not that great for a gamer, and 128MB is wasted on the SiS315 so I'd look for a cheaper version with less RAM.