What I miss the most about 1E is the FEEL of that version of the game. And especially the aesthetics. IMO the writing of 1E was far more flavourful than the dry "computer manual" text found in most of the 3E stuff (and far lighter on tedious stats etc. as well). Gygax had a distinctive and evocative writing style ("gentle readers..."), and the modules written for 1E (whether by Gygax or other early great ones) had a lot of punch to them. Len Lakofka's "Secret of Bone Hill" and Douglas Nile's "Cult" module (N1) especially stand out as great stuff. And the "Giants" (G1-3) and Descent (D1-3) series are legendary.
As for art, despite its occasional technical weakness, I will take 1E art (especially Trampier, Dee, and Otus) over the "spike/goth/punk" art of 3rd edition anytime. There is NOTHING in any 3E manual to compare to the image of "Emirikol the Chaotic" by Trampier in 1E DMG, or the image of the dwarves (and halfling) talking to the magic mouth deep in a dungeon in 1E PH. The original cover for the PH by Trampier (with the thieves in the background prying out the gem eyes from the demon statue) is the Platonic Form of DnD. And Erol Otus' covers for the Moldvay/Cook B/X rules really capture the spirit of DnD better than anything I have seen in 3rd edition books to date.
Hence, as should be obvious in my remarks above, I agree with:
Epochrpg: "...what I miss most about 1e is the writing quality. The modules written in those days actually lived up to some set of standards. 3E mods seem like they were written by videogame designers. Modules like slave lords, lost caverns, and isle of dread are what I would like to see."
Yes, that is right on. Slave Lords and Isle of Dread are CLASSICS. They have a flavour that is vastly superior to most of the current crop of adventures. And 3.x does have a certain "video-game" quality.
And I concur with Teitan's following sentiment.
Teitan: "Actually, yes and no. I am wanting a more rules lite game, after 3-4 years of 3e I am started to get bogged down by skills this and feats that and tweakage of this and tweakage of that and 4 page character sheets and supplement A and Prestige Class Z,X and Y and you get the picture..."
One good thing about 1E DnD is that the variables that the DM had to keep in mind when designing an adventure were relatively limited. 3rd edition can become a strategy game involving feats, etc., instead of operating like a role-playing game.
Criticisms aside, I am running a 3$ Campaign right now, and having a blast. Of course, most of my players played 1E, and so they at least have the proper "aesthetic taste" for my world!