not much of a plot

I agree.

It's a character study.

Duh ! I don't think it's a great film but I admire it for making it's own pace and addressing the angst and ennui it takes many of us to figure out how we fit into this competitive and vapid society. It's somewhat in the mold of Easy Rider, or the more entertaining The Graduate. A product of it's time, but bold for not falling into, oh let's say, the Death Wish model of that era.

I don’t think it holds up to its lofty reputation but there is good stuff in there, especially the great performances of Nicholson, Black and Anspach.

The diner scene is a classic, but otherwise it does seem too aimless at times, even for a character study.