In my opinion, 4E is extremely good as a one-shot game. It is even good as a one-shot introductory game where people don't know the rules.
At one weekend home-based gamefest I attended, a half-dozen or more one-shot 4E style adventures went off without a hitch, covering a variety of genres and styles.
The 4E automatically-generated sheets and cards are amazing, beautiful, very cool -- and ultimately too dense to be practical.
But distilling all of this down to the stuff that actually gets *used* makes 4E into a very simple, fast-and-furious, accessible game that is extremely suitable for one-shots and learning experiences.
The advice I would give would be ...
a) pre-gen characters using the character builder.
b) get rid of the character sheet (or hand it out and immediately slide it out of sight). 90 percent of the stuff on there isn't necessary to actually play, and just gets in the way when you're looking up a value. Instead, just hand out a sheet with the following -- initiative, move speed, the 4 defenses, Hit Points, bloodied value, Healing Surge value, number of surges, skill values, special skill section for passive/active insight, perception, dungeoneering, nature, arcana (the ones which you're always checking)
c) custom-build power cards. use only finalized, pre-calculated values (so they say things like "2d8+6" instead of "2w+STR", so that all of the calculations and math are done ahead of time. Get rid of all the fluff, but *do* distill down the special rules for each power. Re-title the powers if you want to customize them for a particular style or theme (this goes a long, long way to making the game your own, I've found ... when somebody throws down with a nasty-titled power, and writes their own fluff explanation as to why it does what it does, the laughs ensue!)
d) make some extra power cards. For each player, make ... 2 encounter copies of "Healing Surge" with the calculated healing values on them and the rules for defense. 1 at-will copy of "All Out Defense" with the values for that. 1 at-will copy of "Bull Rush" with the rules for that. 1 at-will copy with the title "Do Something Cool!" with an explanation that you're supposed to just make something up -- it'll be okay! -- to remind players that their powers aren't the only option.
Armed with this distilled information and pre-calculated power cards (with extra cards to remind them of the most popular options) suddenly even a higher-level character is play-able with a minimum of advance notice.
...............