The couple was spotted out Saturday grabbing a bite for lunch at the Beverly Hills Hotel, where they were both dressed up in snazzy duds -- BA was rocking a tan pullover sweater with jeans and matching sneakers to round out the ensemble. Nikes, specifically, mind you.

Jen, meanwhile, was wearing a Springtime colorful sun dress and some high-heeled boots.

It's Ben ya gotta focus on, though, 'cause the dude is absolutely radiating ... flashing a big smile to the paps who were shooting them and carrying a little extra pep to his step. The question ... what the heck is he so damn happy about considering his long grump streak???

Besides being married to Jennifer, he's got a lot to be cheery over ... including his latest flick, 'Air,' which hit theaters this week and which has garnered tremendous reviews and stellar word of mouth. By most accounts, it's 2023's first great flick and a crowd-pleaser.

The only (potential) problem is that 'Air' is not on pace to be a box office smash -- especially since it's up against Mario and co., which is taking the top spot this weekend by a mile.

Although his movie is on pace to rake in around $20 mil or so through Sunday -- depending on which projections you look at -- it reportedly cost a fortune to make ... around $90 mil, according to Variety. With that sorta budget, it's hard to say if Amazon Studios will recoup their investment in the short term ... but it's also hard to say what'll be considered a W here.

'Air' is Ben and Matt Damon's first project under their new production co., where they're sharing the wealth, and what's more ... this flick was made with a streaming-first mentality, even though it's hitting theaters initially. So, the formula for success on this one's wonky.