Essential X-Men Volume 8, as you can tell by reading other reviews, is a mixed bag of goods: apparently some fans hate the art, while others hate the stories. Personally, I like them both, but that's because I understand the major complications facing the creative staff at the time, factors which I'll try to simply explain.
First, "Inferno," which is [somewhat] collected in this edition, was NOT an X-book/mutant-specific crossover; it was a storyline which ran through every major Marvel comic, so, like it or not, the writers had to try and make it fit in to what they were doing monthly, and for the most part I feel they succeeded (I seem to be in the majority - "Inferno" reprints only deal with the X-universe elements of the story, ignoring all the other Marvel Universe events).
Additionally, the writers were also struggling to find a way to deal with the resurrection of Jean Grey aka Marvel Girl, who was haphazardly re-introduced back into continuity with the debut of the X-Factor series. Initially - as seen in Essential X-Men Volume 2 (which EVERYONE should own, period, its that good) - Jean's story was resolved, and Chris Claremont went on characterizing Cyclops and the other X-Men accordingly. So, the sudden reappearance of Marvel Girl kind of threw an unwanted kink into the series that wouldn't truly be resolved to satisfaction until the conclusion of Grant Morrison's run on the book. In fact, this Jean Grey "situation" has become a part of general comic book lore, and [...] of innumerable jokes. Bearing this in mind, the stories collected in Volume 8 are an attempt to tie up some embarrassing loose-ends that the decidedly less-sophisticated though deliciously soap opera X-Factor books had already been addressing, and if the results weren't perfect, at least they weren't BAD (like we see later on in the 90's).
Please note: IF YOU DO NOT WANT TO SEE ART IN BLACK AND WHITE, DON'T BUY MARVEL ESSENTIAL VOLUMES AND PLEASE DON'T WRITE REVIEWS COMPLAINING ABOUT IT. These books are deliberately printed in black and white to further reduce production costs, increase Marvel's profit margin, and still provide the consumer a good deal in the age of $3+ individual comic books. Now, with that out of the way, a few words about the art.
If you haven't heard of Mark Silvestri, I don't really know what I can say, other than google some of his work or check out Wikipedia. Anyway, this run he did on X-Men is where he developed his distinctive style and gained national attention. His women are gorgeous, his heroes are ripped, and if you compare his work to other "hot" artists, IMO he's the most competent draftsman out of all of them (Jim Lee included). Dan Green's raw, gritty inking is probably what turns many people off to this particular run, but if you really appreciate comic art then seeing it in black and white serves to better show off its strengths, and make no mistake: Silvestri is strong. His version of Colossus is the undeniable evolutionary next step from Byrne's rendition, and the Goblin Queen...well, she's worth the whole price of admission.
The X-Factor issues here showcase what inking does (or doesn't) do for the penciled art: compare issue 39 - inked by Al Milgrom - with the other issues inked by Wiacek, and you'll see what I mean. Overall, I like Simonson's style, especially his version of the Beast, and have no problem with these issues apart from the Milgrom thing. Anyway, if you left them out the overall story in this collection would be unreadable.
I'm sure this review sounds like a defense of this volume, and in some ways it is intended to be. You can't judge these stories, which were editorially managed and comic-code approved, based on the standards of the truly modern, more mature books of today - you're gonna be disappointed. But if you look at the overall tapestry of the history of the X-Men, taken with X-Factor, New Mutants, and even Power Pack, and compare it with the other books coming out at the time, you see the charm and heart of these stories and characters had. It'll also make you feel the same sadness I did as you watch it come to an end. Because, unfortunately, this group of issues signals the beginning of the end of the X-Men as we knew them; Claremont might still have been writing for a while, but after Inferno, it was just never the same - continue reading past this point and you'll see what I mean. And then of course there was the 90's. Ha, you complain about Inferno? Just wait till they try and "Essential" X-Men #1 and Uncanny 281...or Gene Nation...ugh.
To close, its safe to say that if by the 8th volume you aren't a fan, this isn't for you. Everyone else, just watch the train wreck that is the X-Men at this point and beyond, enjoy the nice art, and take if for what it is - a collection of well-drawn comics. Lee and Kirby it aint, but its still got its moments.