Saints success over a disappointing Hearts side was the first sampled by gaffer Danny Lennon in his two-year spell in charge of the Paisley side.
Previously, Saints had drawn twice and lost six of their previous eight games with the Jambos under Lennon's watch, but Saturday's success takes Saints third in the SPL.
Now Lennon believes he has assembled the strongest Saints squad he has ever managed. He said: "This was a great win and enjoyable for me given it was my first over Hearts.
"I believe we now have the strongest squad I have had since coming here and this result has underlined that belief.
"It was also our first home league win of the season and very pleasing to keep the clean sheet.
"This could be a big result for us and certainly one that has given us a platform to build on and really cement our place in the top six. It was a win borne of a really solid team performance and we will need more of the same at Kilmarnock on Saturday."
Saints can be well satisfied with this comfortable victory and Lennon must be delighted with the cutting edge that has been supplied by the arrival of ex-Newcastle kid Lewis Guy, who scored his third goal in just four appearances for Saints.
At left -back, Paul Dummett also looks like he could be an excellent addition and demonstrated particularly sound positional sense and solid distribution.
While one look at the Paisley bench on Saturday, which included Sam Parkin, Gary Teale and Dougie Imrie, underlined the strength of depth that Lennon has built into his squad.
Lennon also believes that the arrival of Lewis Guy is helping to bring an extra dimension to Stevie Thompson's game with the former Scotland striker outstanding on Saturday.
The Buddies boss said: "Lewis is a tremendous finisher but also a very good support runner. The goal he got with Stevie setting him up was proof of that.
"I look at the bench and we had Dougie Imrie, Sam Parkin and Gary Teale coming off it and to be able to introduce that quality of player in the second period when the game is stretching is fantastic.
"I'd also like to mention young Paul Dummett who was outstanding for us on the left flank. I think he will be a very important player for us this season."
St Mirren took the lead at their home ground with five minutes left to the break, as Stevie Thompson laid the ball back for Saints skipper Jim Goodwin to smash home from 25 yards.
The second-half had barely started when Saints doubled their lead, and the second goal was heavily thanks to Stevie Thomson once more.
The former Scotland striker rode one challenge and ran through another as he charged into the Hearts box before cutting back for Guy to side foot home from point-blank range.