In my one playing of Waterville I felt it was a difficult course that a good and smart player could get around quite successfully. But that also mean the average player will inevitably find themselves in a sticky situation where they make a very bad decision.
During my round the wind was coming from the South, such that while playing the 18th, the wind was coming from ~2:30. With the 1st and 2nd playing almost straight down wind the course did not seem difficult and it was around the 4th or 5th that our caddies told us that the wind direction was opposite of normal. What I appreciated is that the course was well protected for both the typical and atypical wind. The fairways are more generous that many Irish links, which may make the course feel not overly difficult, but it still seemed fairway position was key. Also, playing 16, 17, & 18 with the wind howling off of the right and having to play your tee shot over the water is a pretty scary and difficult proposition, which may have tinted my impressions.