I've seen a 1 star review of a decent restaurant because "they didn't fill my water glass often enough" -- no other complaints. Sometimes you pay enough for this kind of service, but most restaurants (especially the ones that take a risk on a new server) are going to have bad days.

That said, any bad service or review during the early days of a restaurant are impactful on long term revenues. The slope of the curve in the early days has a bigger effect on the area under the curve.