A bit of a late post, so most of you have probably seen this already.
It looks like the cheapest virtual only buy in for the full game is $150, while the cheapest physical full game is $195 (+shipping/import tax!)
There are some links in there for some early reviews and play-throughs too. These only look to be the Stormlight system though, so I assume the Mistborn/Scadrial (an any other planets) are still in the works.
It sounds interesting although unfortunately I've only read the first Brandon Sanderson Mistborn book. Maybe getting the rpg would encourage me to finish the rest of them lol.
I suspect the adventures that come with it will have a degree of spoilery-ness, but its definitely an extremely interesting set of world settings (particularly Stormlight/Roshar) if you wanted to use it in a campaign using a different system.
I would obviously recommend reading the books, the first couple of Stormlight books are awesome if your fine with a slow start. Unfortunately I think the second Mistborn book is considered the weakest of the series, still good though!