Ya, and my friend D-Tension the rapper is in it as an uncredited extra. Without giving away any of the plot (which is cliche and predictable anyway, it's a typical romantic comedy), he is the short, fat, bearded guy with glasses who is standing on Tina Fey's left during the "Pizza Box" scene. There are also a few local comedians that my husband knows, one of them is this Chinese guy whose name I forget, and he actually has a few lines.
But Lowell looks awesome - they even show a shot of the SUN sign. If you stay to the end of the credits, it says "Thanks to the City of Lowell" at the very bottom.
Here is another movie that was made in Lowell by D-Tension and his partner Effect (Los Wunder Twins del Rap):