Whizbang Dustyboots said:
I disagree. The 3E edition incorporates a lot of tweaks to the setting that Planescape's scrutiny on the planes gave us, minus the cant and the focus on Sigil. In contrast, a lot of the 1E stuff is ill-defined, since it was primarily about establishing the basic vocabulary for anything beyond the simple, simple stuff in the PHB and Deities & Demigods.
Exactly. A lot of material on the planes in 2e, and even 3e, has changed them from the conceptions back in the 1e MotP. For instance, the upper planes are virtually without inhabitants in the 1e MotP (there's talk of 'good spirits', and the beings later codified as aasimon/angels, and the archons are there in the back of the book in an appendix), but two of the primary celestial races (Eladrin and Guardinals) didn't exist till later in 2e. The Outlands in the 1e MotP lacks the Rilmani, the Infinite Spire, and Sigil, etc.
Don't get me wrong, I've got a copy of the 1e MotP sitting on my bookshelf, and I won't say it's a bad book (not at all, it has some nice ideas, but it didn't give a lot of in depth details because it was the first book to really touch the topic and it had to be broad). That given, the book does have to be viewed in light of the fact that what detail it does give has since been superceded and expanded upon by the later sources: the 3e Manual of the Planes gives a very good overview of the planes as they have developed since then, and if you're looking for more specific detail there's the various 2e Planescape sourcebooks and for the Abyss there's the 3.5
Fiendish Codex I.
Edit: The 3e Manual of the Planes is one of the best 3.x books there is, and because of how broad it is, it's one of the few books to see use in each game session I run. One or two superficial changes it made from 2e I didn't care for, but no book is perfect.
The 3.5 Planar Handbook isn't all bad. The first 2/3 of the book are pretty good, the monsters are nice, and the details on Sigil, the City of Brass, and Tun'arath are nice if somewhat dry in tone. The only bad part of the book is the way they handled the "planar touchstones", about 30 odd pages worth of them. Though some of the locations were nifty ideas, the implimentation of the concept came off poorly, making locations of mystery and intrigue come off as so many planar powerups like aasimar Mario might collect a fireflower and spit fireballs at Githyanki, etc. So the book isn't bad, and I've marginally warmed to it over time, but it fell short of what it could have been if so much space hadn't been used on the touchstones.