Is XM weather worthwhile?

My SR22 partners want to install XM weather to the tune of about $10k.
I'm not convinced it's worthwhile. The plane is based in Southern
California where we don't tend to get the kind of squirrelly weather
they get east of the Mississippi. In the summer we'll get isolated
thunderstorms over the desert, but the plane already has a stormscope.
We get marine layer fog, but XM doesn't help with that. The only
situation, it seems to me, where you'd get any use out of it at all is
if you're flying in a winter storm, which I something I never intend to
do (and they're pretty easy to avoid because they sweep in off the
Pacific and can be reliably predicted days, sometimes weeks, in advance).

Does anyone out there think XM weather is worthwhile in SoCal? If so,
why?

Thanks,
rg