If the flight is cheap and the timing convenient I'd say go for it! Invest in some earplugs, an eyemask and a blowup neck pillow. Then they can try and sell to their hearts content without disturbing you. Priority boarding is an advantage too as it's easier to sleep with your head resting against the fuselage. This is what I do if I'm catching a 6am flight (which involves being up at stupid o'clock to get to the airport).
I'm not sure how much Wizzair will try to push inflight sales on this particular flight but normally they tend to be a little less intrusive than the likes of Ryanair or EasyJet.