This is an interesting film, all the more so because it is meant to tell a true story (insofar as any film of real events is true!)
I suppose you'll either like it or loathe it. If you like it, good; it isn't a bad film, but a bit of an idea of European history will help you.
If you you fall into the latter category loathe it because you think it's a bad film not because of the stupid bigotry shown in some of the other reviews here which seem to be so hung up on the USA and Mom and apple pie that they see "Commies" in even thinking about the event of the early 20th century!
After seeing it it made me interested enough to find out about John Reed. You might not like what he thought, you might not like Warren Beatty and what he thinks but for heaven's sake don't rubbish this film simply because it's about a political system you may not like, or have been indoctrinated not to like!
It's not brilliant but neither is it a "love poem to communism".