It's this latter point I'd like to focus on. Now, I love module B1 and I've used it many times for new players; it has lots of fantastical elements that really grab your imagination. But the design is radically different from the later B2, and I wonder if Gygax's desire to replace it isn't partly due to a difference in design philosophy. Just for starters: B1 is much easier than B2 in terms of monster numbers and tactical toughness (a small group that gets through B1 easily will be chewed up and spit out in the first encounter of B2). Secondly, the dungeon layout: B1 uses the older every-square-used design (i.e., pen-line walls), while B2 uses the later no-adjacent-squares design (i.e., 10' walls). Thirdly: B2 has themed monster lairs, with several areas populated by the same type, while B1 will have unrelated monsters scattered in small numbers throughout.
But perhaps the more important thing is the level of detail given to the area dressings. The B1 area descriptions are very long, with lots and lots of minute setting detail. That's great and gives a wonderful sense of place, but it seems exactly the opposite of what those of us in the OSR have taken to using, with our minimalist dungeon descriptions (and some acclaim for one-page only dungeon designs). Even the monsters and treasures in B1 are really afterthoughts, one-line notes to be filled in by the administering DM, with the area dressings, tricks, and traps really the centerpieces. This is also counter to the sensibility of module B2, whose area descriptor are very short, and focus primarily on the monsters and treasures therein, with relatively little in the way of dressings or tricks.
As a specific numerical comparison, surveying the first twenty encounter areas in each module: B1 encounter areas run an average of 36 lines long (stdev 27), while B2 encounter areas average 12 lines long (stdev 8). So on average, it appears that B1 encounters are 3 times longer in the description than B2 -- and that's not even including any monsters or treasures yet for B1, to placed by the individual DM!
So, what do you think? Was B1 fundamentally a misstep, showing neophyte DM's a setting design that was enormously more labor-intensive than is either required or used by experienced DM's? Or was it useful to show the maximum level of detail and trap/trickery that anyone might ever encounter? Was Gygax correct that it needed replacing with a more basic dungeon design as a starting example?