In the Springfieldian dialect, I'd call it cromulent entertainment.
In fact, it was somewhat surreal to watch a movie like this in a theater setting. The comedic elements were met mostly with light laughter that was the guffaw equivalent to the "golf clap". While the one or two genuinely laugh out loud moments appeared to be too subversive for most of the audience.
The plot was pretty much a supersized version of 99% of the usual "Simpsons" small screen storyline: Homer screws up. The road to redemption tweaks the noses of familiar pop-culture and political targets (a scene with a room full of government eavesdroppers pays off nicely), but ultimately, if you've been watching the seminal series since the beginning, you'll find yourself sifting through moments during the movie that have been recycled from earlier events in the TV show.
That's not to say I was disappointed.
My expectations were low enough that I hemmed and hawed and bought a bootleg "studio copy" a few weeks back that turned out to be a different (yet, equally underwhelming) animated movie, instead.
The Simpsons Movie killed about 80 minutes of an otherwise lazy (and f*cking hot) Saturday in San Diego and, on a grander scale, served as something of a (belated) victory lap for the writers and producers who were told back in 1990 that going up against "The Cosby Show" was sheer lunacy. On these levels, I had no problem with the flick.
But, you should still just wait for the DVD.