I have been reading a book about them recently, so I have some feelings. On a general level, they were revolutionary socialists opposed to dictatorships like Soviet Union and China, so basically the good type of socialist if you ask me. It seems that they generally were critical of state as a concept, although I am not sure how critical exactly.
On a more specific level, their theory of spectacle is quite hard to understand for me for some reason, but I think it basically says that the society makes us passive consumers of commodities and propaganda, which seems like a reasonable criticism.
Also, reading about them has strengthened my wish to found an anarchist avant garde art collective.