Anyway, I was thinking about Planescape and how I feel about it and decided to give it another thinking-over. Here's what I came up with after reading through the campaign setting box set and the Planes of Law box set.
First, I'm still (after all these years) pretty much ambivalent about the setting. What do I like about it? Well, first of all it's a very consistent setting - every product pretty much follows the same feel, the same atmosphere of the whole.
The information is well detailed and expands (somewhat) upon the information for the planes given in the 1E Manual of the Planes. The art, though not my all time favorite AD&D art, is still for the most part very good and entirely consistent (and much better than the travesty known as Dark Sun, with its amazingly gorgeous Brom covers that only serve to make more disappointing the hideous Baxa art inside!). The art sets the mood and it's very consistent.
There are some very cool new monsters (rust dragons, marraenoloths, etc.). I've always loved box sets, so that's a plus too. Overall, it had good and consistent production standards.
On the other hand, there's much I don't like about it. First, the cant. The annoying Victorian-England slang that, while funny and entertaining, comes across as too real-world, outdated, and humorous for the setting. It's like comedy in horror movies - it takes away something.
It's also far too wordy. Sure, the read is entertaining, but the excess verbiage (all written in that disturbing "cant"), often obscures the relevant details. I often find myself thinking - "Ok, ok, I get it! Ha, ha! Now get to the point! Too much of a good thing, etc.
One of my biggest complaints is that they left out so many major powers and (in)famous AD&D characters. Tiamat, one of my Top 3 Villains of all time (along with Orcus and Halaster), is barely mentioned in the main box set where it details Avernus, and in the Plane of Law box set where it looks at the Nine Hells and Avernus (the first layer, where Tiamat plays a major role) in detail, Tiamat is not even mentioned!


Likewise for Orcus. They replaced him with that idiotic Kiarnasalee thing, then later brought him back and turned him into Tenebrous. Look, Orcus is one of, it not THE, most popular AD&D villain of all time! Why screw him over and get rid of him like that? I thought that was utterly stupid, and I know plenty of old time gamers who grew up dreading Orcus in the game who really, really hated the fact that Orcus was passed over.
Likewise, Asmodeus, another of the most popular villains in AD&D history, it not detailed. At all! Worse yet, they made a very strange and idiotic decision to not detail certain arch-devils on certain layers, omitting some of the toughest such as Baalzebul and Mephistopheles. Why? It's no secret to anyone who's ever played the game who rules what layers. It didn't come off as cool and mysterious to me - it came off at stupid. It's like saying - "Well, the Greek pantheon has a lot of gods including one we won't name who rules them all and casts lightning bolts."

It also got expensive, seeing as how there were 6 boxed sets, of which 4 were necessary to cover all the Outer Planes, while the Astral and Ethereal Planes got only a single book each, along with a single book for the Inner (Elemental) Planes. At $30 a box set, $20 for the Inner Planes book, and $17 each for the Astral and Ethereal Planes, that comes to $174 for the setting, plus another $46 for the two Monster Manual books for the setting, which comes to $220 for everything you need to play. Adjusted for inflation, that's $382 in 2020 dollars. Quite a steep price tag!
It's also a pain in the ass to find information because it's spread out between no less than 8 different products (4 box sets, 3 books for the Inner/Astral/Ethereal Planes, 2 books for the planar monsters).
Without all that excessive verbiage, they could have pared it down to say a 200 pg. book and sold it for $50 and called it a day!
Finally, I don't like how they introduced Sigil and turned it into the cantina scene from Star Wars - with pit fiends, solars, and all other sorts of antithetical beings all getting along. It made the planes too mundane with all the towns and Borderlands and so on. I never saw the planes as a place to use as a setting. It was always just a group of deadly places to visit and therefore all the most exciting and mysterious. To me, the transition from Manual of the Planes to Planescape was a step down, something that detracted from the challenge, mystery and charm of the planes as detailed in 1E.
So yeah, after all these years I think it's a great read for pure entertainment, a good source for some new monsters and it has some more detailed rules to a small degree. But to me it's best used to mine ideas and inspiration. I never could see the planes as a place where low- (or even mid-) level characters go traipsing around.