I remember when this film came out... I was an Altman fan then but I could never convince any of my friends to go see this with me (I was in high school at the time). Twenty years later I finally catch it on Bravo, and found it well worth the wait (and boy am I glad I popped a tape in to record it).
The acting in this film is superb, as is the direction (as you'd expect). Altman has taken a stage play that takes place on a single set and brought it to the screen in a way that manages to preserve the theatrical ideosyncracies (e.g., the actresses don't change their appearance, or even their outfits in some cases, in flashbacks to twenty years earlier) while still being masterfully "cinematic" in the way Altman composes his images.
If anything, the Achilles' heel of this movie is its script, which appears to be taken verbatim from the original stage play. There were times, especially towards the beginning of the movie, when it seemed somewhat awkward, but in a way that probably wouldn't seem as out-of-place in a play. I guess that's why they call it "stagy". But still, it's a minor complaint, and the great acting and compelling story more than make up for it. Overall I give this movie an 8/10.
