Williams hadn't scored for Wales since touching down against Australia last November, so it was a relief all round when he pounced to take his tally to 48 Test tries with Wales.
Gatland said: "I think the first one he made a little bit more difficult for himself than he could have but it's great to see him making a few breaks with the ball in his hands. It's great to see him playing with a bit of confidence again. It helps any team if they have players with the X-factor.
"We are fortunate to have two or three in the side and Shane is definitely one of those. Shane is a very talented player. You need players who can create something out of nothing"
Gatland also singled out Stephen Jones, who finished with 17 points. "He's like a good red wine, getting better with age," said Gatland, before adding: "Overall I am very pleased with the performance. We felt that we are making some progress."