If you like reading stories where every major characters ignores their established personality and ideals to serve the writer's big idea plot, then you might like it. However, I think Millar is a terrible writer with no regard for the sandbox he is playing in or anything previously established about shared sandbox characters and does what he wants regardless. The only reason characters act the way they do in this story is because the plot requires them to, not because it makes sense in the situation, not because it is how their character has been established over the years, not because it is how a sane human being would react in those circumstances, but because that's how Millar wanted/needed them to act to serve his plot. This is the story (in conjunction with Final Crisis launching at DC) that got me to stop reading not just Marvel comics, but all comics for nearly 5 years as I had no desire whatsoever to walk into a comic shop of pull anything out of my boxes or shelves to read after reading it.

Unfortunately it sold well and became a phenomenon with a younger generation of readers and reshaped the landscape of Marvel in particular, but comics in general in its image, and keeps getting revisited time and time again.

When someone asks me what is wrong with modern comics, this is what I want to point to as the easiest answer. There is a lot right in comics today, but a lot wrong, and this is the epitome of the wrong parts to me.

-M

Pretty much hated it for the same reasons mrp mentioned. The basic idea was interesting, but Millar just arbitrarily had the characters do what he needed them to do for his plot. Many major characters acted completely and totally out of character. And then these bizarro versions became the new status quo going forward. For me, the real Marvel Universe pretty much took a bullet to the head with Civil War. I essentially stopped caring about anything in the MU after almost 25 years as a fan thanks to Civil War and the new status quo that followed.

Marvel basically took the biggest a-hole writer in comics and let him write the entire universe in his image. No thanks. 

The damage that it ultimately did to the Spider-man franchise ended my interest in the character. Take from that what you will.

If you read it as an elseworld kind of story and avoid most of the tie-ins it's fairly interesting story but its massive size and mis-characterizations made me drop Marvel at the time. For my money though I'd suggest picking up Planet Hulk, it has the modern epic feel but it stays true to the who the Hulk is and has no tie ins.

Civil War seems to be pretty much applying what had already been done better in other comics like Watchmen and The Authority to the Marvel Universe. I'm just not sure that level of cynicism really works for me with the classic Marvel characters. I'd file it under interesting but really flawed. There are some scenes that are kind of important that are not in the actual Civil War mini-series, so I think it is not a very good read in the regular trade.

I'd definitely vote Planet Hulk and Annihilation as being much better 'big' series from the same time period. Those two were really good, definitely in my list of best Marvel stories of this modern period.

Annihilation is the best event comic that Marvel has ever done, and we got three years of excellent cosmic stories from it.

I love Planet Hulk itself, but the follow-up crossover, World War Hulk, was a massive disappointment for me. This was a story that needed to be told, but it really dropped the ball, despite some cool moments like Dr Strange invoking Zom.  DC's version of this would be Blackest Night, which completely squandered all the momentum that had been building from the very good Sinestro Corps War.

At least World War Hulk gave us the Incredible Hercules series.