But what did we learn about West Ham from the match?
1) West Ham must improve their game management
The Hammers have thrown away leads in so many games this season and in real terms it has cost them around 10 points.
A lot of that has been down to poor refereeing decisions going against Bilic's men but as a unit West Ham have also not protected leads well enough.
Even against Watford's reserve side the East Londoners wasted a host of chances to put the game to bed and allowed the visitors back into the game.
Watford could have made it a nervy final few minutes too but Troy Deeney's late spot kick was saved by Adrian to preserve the two-goal cushion.
Against Leicester City at the weekend Enner Valencia carelessly gave the ball away deep into stoppage time rather than playing it in the corner and West Ham gave away that controversial penalty to throw away two points.
It has been a fantastic debut season for Bilic but game his side's game management must improve if they are to progress next season.
2) Carroll like a new player
Andy Carroll is on fire at the moment. The big striker has five goals and an assist in his last three games and is knocking on the England door again ahead of this summer's European Championships.
But it's not just his goals, ask any West Ham fan and it is Carroll's fitness, desire and tireless running which make him such an asset.
He was everywhere against Watford and was unlucky not to be awarded man of the match.
One moment which summed up the kind of form he is in came in the first half when he controlled the ball on the right wing beat a Watford player and fizzed a sublime 40 yard cross-field pass to Dimitri Payet who almost scored.
The pair shared a laugh afterwards along the lines of "That's usually the other way around" - a joy to watch.
3) Michail Antonio is running Payet close for Hammer of the Year
Dimitri Payet will probably win the vote for the prestigious Hammer of the Year award hands down, particularly given he has been shortlisted as one of six for the PFA honour.
But Michail Antonio, West Ham's most sung about unsung hero, is surely running the French star close.
Once again the former non-league star was absolutely superb as a makeshift right back.
Antonio has been so good he is now keeping two proper full-time right backs out of the West Ham team.
His defending is top drawer and his endless stamina up and down the right mean he still offers an attacking threat too.
He won the second penalty with a brilliant bit of skill taking on three players on the right and rampaging into the box.
Hammers fans love their grafter and he at the very least deserves to be runner-up. And to think before West Ham's injury crisis at the beginning of the winter he could barely get a look-in. Now his one of the first names on Bilic's teamsheet.
4) Lanzini needs to work on his finishing
Manuel Lanzini has been a revelation since signing as an unknown quantity from the footballing backwater that is the UAE League.
But the diminutive Argentine has been a little below par in recent weeks and was dropped for the game at leaders Leicester City.
He returned to the starting line-up against Watford and showed some lovely touches but was guilty of wasting two glorious chances to put the game to bed.
That could have cost West Ham as Watford briefly threatened to claw their way back and Lanzini must work on his close range finishing to progress further and become a true Hammers hero.
5) James Collins is better than Zidane... apparently
Not only is James Collins likened to the great Pele, now he is also better than France legend Zinedine Zidane.
That's according to Hammers fans who welcomed one of their favourite players back from injury with a series of stirring renditions of songs dedicated to their Welsh warrior as he warmed up throughout the 3-1 win.
"One Ginger Pele" rang out several times as the West Ham faithful showed their appreciation for a player close to their hearts. And that was followed by several choruses of a new chant for him using their famous Payet song.
"We've got Pele, Ginger Pele, I just don't think you understand.
"He's super Slav's man, he's better than Zidane, we've got Ginger Pele."
Surely the chant of the week...