I tried to read this in the context of when it was written, rather than compare it to more modern fare. I part listened, part read my way through it in a relatively short space of time (for me) and didn't really lose my way much, though there were a couple of times when listening that I had to go back.
That said, I did find the characters two-dimensional, and at times acting contrary to character for no good reason. I should have made notes at the time, as it's a month since I finished it and I'm finding it difficult to remember specific examples (I mostly listened to it, so taking notes was out). I did find Dartagnan an engaging character, with his youthful exuberance and naïveté, and his unswerving loyalty to friends and the cause (except when he change alliagence

). I read it mostly as a comedy, so wasn't particularly disturbed by the way they treated eachother, though at times did consider it a bit heavy-handed.
Dumas didn't go to the writing school of "show don't tell", that's for sure, but I put that down to the time. He breaks the 4th wall quite frequently, which I took as an attempt at humour, and mostly it worked.
I felt that I missed a lot of the references, not being well acquainted with this period in French history, and that I might have enjoyed it all the more if I was more aware of certain historical events.
Unlike some, I found the character of Artemis somewhat tedious. His pious leanings did not seem to sit well with his actions at times, and I couldn't really see why an overtly religious man would want to be a Musketeer.
As with other reviews here, one thing I couldn't quite understand was Milady's cowardly collapse. At first I thought it was a pretense, and she'd suddenly reveal her devious plot. Quite went against the grain of this powerful character, what with her pleading that she herself is "too young" to die (despite having just poisoned Constance).
Did I enjoy it overall? Yes. I think listening to a well-read story helps to gloss over some of its failings. Will I read any more in the series? Probably not.