I think they're going to really struggle. As they always say when a team goes up to the PL, the top division will punish you - at the lower levels you can get away with letting chances go, at the top level you have to score the chances you get or you're going to miss out. Watford have now gone two games already without scoring after their first game, and they've been lucky that they've managed to draw every game, but if they don't get the goals then they're going to go straight back down. More than a few pundits have been asking where the goals are going to come from this season, and unlike Bournemouth, I'm just not sure people see enough goalscorers in that team.
Incidentally, I'll be in Manchester for the Watford game this Saturday, so I'll get a first-hand view of just how good they are against a stronger team. Kind of funny that I'm travelling 150 miles and I'm going to end up watching a team from 20 miles away from where I started, but there you are.