To clarify, the free demo limits are per pair. You can demo all day, you just have to swap pairs every 1.5 hours. You might get a pair from Fanatyko or whereever for the day, but also checkout the free demo tents and take a couple runs on something else, too. That way you won't be stuck if you get back to the demo tent and they are out of everything you want, and you'll get to check out more than one ski in a day without busting the budget or going back to the base to swap.
I'd waste Saturday. I think it's going to be absolutely mobbed, given the forecast and how desperate we all are. We've set aside this weekend for a last minute, based-on-conditions trip, and I'm picking Schweitzer instead of Whistler, even though it's further and the forecast isn't quite as amazing, because I think Whistler will be insane.
Actually that's a good idea - to get a pair for the day and swap off what's in th etent. Also, they're usually pretty lenient if you come back a little late, or ask nicely to keep something you really like.
Going up to WB Friday afternoon. After the disaster that SLC is right now (didn't even bother going out today after looking at the bases of my skis from yesterday, actually having some snow (without rocks) would be a nice change. Yes, it'll be a cluster, but it's been a long time since decent snow.