The best way to make a single, flavorful, consistent cup of coffee that I know of-- without much hassle or clean-up required.
Positive Product Points
Simple and fast way to make a tasty cup. Easy clean-up. Perfectly functional and durable. Everything is under your control when brewing. Good for high-altitude brewing where you can't get to 200F for "normal" drip brewing.
Negative Product Points
Despite box claims, does *not* make espresso. Design is function over form; has a "what-the-heck-is-that?" look. A layer of grinds often stick to the plunger when emtpying, so that you'll need a wiper to get them all off. You'll need to get special filters when the 300 or so that come with the device run out. (Note that none of these are very serious negatives in any respect.)
The Aeropress is an easy-to-use, sturdily-constructed apparatus for making one to four servings of coffee. It leaves almost all variables (grounds, water temp, water amount, steeping time) under your control when brewing a cup. The non-brewing parts of the coffee-making process are what take the most effort when making a cup: I am usually waiting on heating the water or grinding the beans rather than the actual brew itself.
The Aeropress is basically a large plastic syringe, complete with large rubber-ended plunger; instead of a needle at the end, there is a screen over which you place a paper filter and attach to the bottom. Once these are in place, put the grinds into the bottom of the cylinder on top of the filter, fill to the desired level with hot water, stir with the provided stirrer, and put the plunger in the top. Wait a short time, or not, and then press the plunger. Concentrated, flavorful, smooth coffee flows out the bottom. Drink as is, or add more hot water for a more normal drip-brew strength.
When the box says "cups", it means espresso-type demitasse cups, of about 1.5 or 2 ounces each. The cylinder doesn't hold a whole lot of water at once. Though I haven't measured, I'd say it's about 8oz with the grounds, and the sides are marked with suggested levels for servings. The box also comes with some detailed suggestions as to water temperature, amount of water, amount of grounds, fineness, and so forth. Please realize that you can break these rules if you like, and please don't be hoping for a true espresso. It's not even like a mokapot espresso; it's a different drink more like really good strong drip coffee-- which, when you think about it, is exactly how you are preparing it.
The suggestions say use water temp of 175F; a break from the SCAA snobbery, for sure, but this temperature produces a much less bitter brew. Personally I find that 185F makes for a better cup. The cylinder has marks for amount of water per serving; I break this regularly by using slightly more. All the variables are under your control, and honestly I am still experimenting with them. More water, higher temperature, coarser or finer grinds, precise following of instructions or not, adding water afterwards, not adding water afterwards-- you get the picture.
My own suggestions and notes:
Use a fine grind, although you don't need espresso fineness. I grind at notch 3 on my Baratza Maestro for 2 cups, 0 for 1 cup. You can use a coarser grind with a longer steep.
Squeeze the grinds as hard as you can, a lot of flavor seems to be in those last drops.
Please note that the foam that comes out is not crema in the true sense; it's just bubbles. They disappear in less than 20 seconds.
You'll need a sturdy cup or mug to receive the brew from a hard squeeze; don't use your dainty bone china or one with a narrow bottom.
Experiment with water temperatures, grind fineness, amounts and other variables and see how the taste profile changes. Find what works for you.
Watch out for bloom when pouring in hot water; it will reduce your plunger capacity. This is common with freshly-roasted coffee. I often get 1.5 inches of bloom from a fresh batch.
175F is a hard temperature to gauge by eye. If you're starting to see bubbles on the bottom of the heating container, it's probably already at 185F or beyond. You'll need an accurate thermometer or thermocouple measurer if you're fastidious about this.
What comes out is concentrated and highly flavored. You'll probably want to add more hot water, outside of the press, if you're used to drip coffee. But it can be fun to drink as-is, too.
Clean-up is easy: pushing the grounds out of the bottom tends to produce a "puck" similar to an espresso portafilter, and a soap-and-water washup is not really necessary. However, I always seem to get a layer stuck to the plunger, which I have to scrape off with a paper towel or my fingers. My occasional sloppiness also means I tend to wash it about every two or three uses, because I've got grounds or brew somewhere I shouldn't.
The filters are simple, and look inexpensive enough to replace cheaply. You could make a more permanent cloth filter if you want, I suppose, by cutting out a round of appropriate material. I'll be trying a Yama cloth filter soon to see if that works too; but it must be able to handle the finer grounds that you'll want to use with this product.
Sweet Maria's was as stellar as always.
Three Month Followup
I am surprised how often I use this device. I own a TechniVorm, a Bialetti moka pot, a Yama vacuum brewer, as well as the Aeropress. I wind up producing about half of my morning brews with the Aeropress; the TV is about 45%, and the other two total maybe 2%. (The remainder are either purchased or provided by someone else.) The ease of boiling water and grinding coffee and not much else required makes it a frequent choice for the morning. And it makes for a mighty tasty cup, with a mellower but more fully flavored brew than the TV.
I haven't taken it on any trips yet, but it would be my first choice if I could be guaranteed a good grind.
One Year Followup
I've cut back on using it, to about 5% of my morning cups. However, it has shown no wear and tear, even after running it through the dishwasher on a semi-regular basis. This is apparently a for-life purchase :-). I'm more likely to use it when I'm almost out of beans, as I can grind super-fine for a deeper extraction and make the most of my meager single scoop. It's also good for a quick single cup as you're heating less water and usually to a lower temperature.
I've read posts of some who use this as a sort of "reverse French press", where the device is inverted, allowed to brew for some time, and then inverted and pressed normally into the cup. I find this approach non-optimal, as when the device is inverted there is even less room for water and grounds in the cylinder than when right side up: a) the filter cap actually provides extra room on the bottom when RSU that is not available when USD, and b) putting the plunger in place takes up some additional room on its own.
A perhaps better approach but one that requires an additional container is to infuse in a separate cup and then pour to filter through the device. The second container then should only need rinsing. It is more messy, but allows for more optimal infusion volume.