B2's purpose is to introduce new DMs to the game (beyond what is found in the Basic rulebook itself) & provide them with a starting setting & encourage them to flesh it out. In this, it does admirably well. It gives them a home base. Shows them how to detail it further. It gives them a bit of wilderness, a handful of side encounters, & opportunities to flesh them out. It gives them a pre-stocked dungeon with a lot adventuring potential. While the rulebook gave lots of advice on creating dungeons, B2 gave a concrete example orders of magnitude more useful than the example dungeon in the rulebook.
I agree with Dr. Holmes who said it was the best work Gygax had done ("for us") to date.
It's easy to find "illogical" elements in any module, especially one that intentionally doesn't bother to spell everything out for you. It's equally easy to come up with rationalizations for any such criticisms.
One of the best things about this module is how it encourages roleplaying. The module may be "about" hack & slash, but when people tell stories about B2, it's usually events in the keep itself that they highlight.
For me, this module has a lot of qualities that I wish designers would emulate. It tends to give me the stuff I need & leave out the stuff I'm willing to improvise.
Rumors! 'Nuff said.
It doesn't give me stupid NPC names (i.e. anybody else's idea of fantasy names except my own) that I have to choose to either suffer with or try to replace. For some reason it's much easier for me to add a name to the occupation used in the module than to substitute names. More importantly, I don't have to know the name of an NPC until it actually comes up in play. I find the way this module refers to NPCs by occupation instead of name makes it easier for me to follow when an NPCs is mentioned in other contexts besides where he's likely to be encountered. ("Blarth?" ...mad flipping through module... "Who was that again?") This is something I hope to emulate if I write any more modules intended for others to use.
It doesn't have pages upon pages of prose that I have to sift through looking for the relevant nuggets. I don't have time for that these days.
As for the home base & environs aspects of the module, these are good things to emulate, but I don't think every module needs them.
While I find a lot in the module to be exactly what I look for in a module, I recognize that somebody else's needs may be different.