X is such a clusterfuck, but I love it.
It's a manga that is full of really godawful storytelling and convoluted plots and intentionally vague/misleading developments, but it's just so goshdarn epic that I can't help but like it.
If you're not a fan of apocalyptic, dark fantasy tales where everyone dies because reasons (read: angst), then X isn't for you. If you're not a fan of Clamp, I doubt X will make you a believer, unless you are a fan of philosophical mumbo-jumbo coupled with the end of the world and people dying everywhere.
It just so happens that, while I am not a Clamp fan, I am, in fact, a fan of philosophical mumbo-jumbo and people dying a lot. It's great. I couldn't have picked a better series to trudge through.
Now, for those willing to give X a try, the first few volumes are admittedly a pain to read. (Yeah, the first few volumes. Just goes to show how long this series is.) But after Kamui finally makes his choice, things really take off, and everything goes batshit. It's fantastic. Also, lots of blood and gore, which is always my idea of a good time, so.
The thing about X is that you have to be willing to be charmed at the beginning. You have to accept this apocalypse and magical "Kamui" bits at face value. It isn't quite suspension of disbelief, but it's something close. Basically, you have to go into X willing to believe it truly is an epic tale of humanity vs. nature. Because the most fun part of X isn't the premise or the characters (though laughing over character motivations are pretty funny, I'll give you that), it's really the philosophy that comes with it. If you just accept everything else about the plot, the philosophy becomes much easier to digest and contemplate. And even if some of these philosophical ramblings don't make sense, they're great fun to think about, that's for sure.
Otherwise, yeah, while X is certainly Clamp's most ambitious work (and I think Clamp pulls it off here far better than in the cringeworthy Tsubasa), it's certainly not their best or their most thought-provoking. That honor lies with both Tokyo Babylon and Clover (Clamp). X is probably the most interesting of their works, though, and the most fun to pick apart (in a good way; Tsubasa is the most fun to pick apart in a bad way).
P.S. Yeah, that ending cliffhanger is excruciating. Though, at this point, I suspect Clamp hasn't started this up again because they've written themselves into a corner and doesn't know how to end this. They've never been good with endings (I can think of only two series from them, tops, that have ended at least decently). So, from that perspective, the hiatus is a blessing rather than a curse. I would rather have an inconclusive "to be continued" for an epic of this scale rather than a terribad ending.