I'm thinking that canceling wouldn't help you.
I can not blalme them for wanting to stay safe - in fact I feel for them and their ability to pay their bills given this weather!
And I've seen no indication that they're slipping their quality due to this short term problem - I suspect that they'll ship only "TBS quality" rock as they get it available. It'd be a huge mistake on their part to allow themselves to ship "lower quality" stuff due to a short term weather situation.
But then again it's their business, not mine - but if it was me I'd send an email stating that I was willing to wait for "good stuff", to make clear that time's not your most important issue.
At any rate puling your order doesn't seem to be a likely way to get the LR you want - unless you're going to a different vendor (and I can't see how their weather's a lot different then the weather for the TBS folks). And from what I can tell there's no vendor out there quite like TBS...
Just my $0.02 this Saturday night...
- Michael