Depends on the purchase price. If reviews are integrated and I don't have to load up several browser tabs and go searching/digging, then I'd look at them, and give them weight, of course.
If the purchase price is above a certain pain threshold, where getting nothing, or poor quality products/services would cause me serious grief, then yes, I'll check their reviews, and make sure I use a payment type that can be reversed if they don't deliver as promised. Either that, or I push hard for pay upon completion or escrow so that both are protected.