I was really anxious about trying this coffee maker. The promise of evenly extracted grounds at the perfect brewing temperature with the convenience of an automatic timer sounded too good to be true. Well, it was.
The first problem I encountered is that if you fill the pot to the 12 cup line, water will be forced from the pot up into the brew chamber when the brew chamber is attached. Essentially, you push the brew chamber down another half inch once the rubber seal makes first contact. This forces air into the pot, which forces water up. Your grounds will get wet with cold water and soak until coffee is brewed, which is not a good thing if it will sit overnight. This also means that any warming of the water will cause more water to enter the brew chamber above. I suspect that even the gradual warming of cold tap water to room temperature could cause this, but I didn't test that theory. The solution is to use less than 12 cups of water... 11 should work.
The next design flaw (and perhaps the biggest) has to do with brew temperature. As the water heats up and steam accumulates in the pot, water is forced up the tube to the brew chamber. Unfortunately, a significant amount of water makes this journey when the water is not hot. The last of the water entering the brew chamber may in fact be the optimal temperature, but unfortunately, it is mixed in with the existing water that clearly isn't. I used a candy thermometer to measure the water/grounds mixture. I had a low reading of 182, and a high reading of 185. I was able to get a reading of 195 from my old Krups, and about 210 from boiling water. The thermometer is reasonably accurate, but a little slow.
I don't understand why people claim the vacuum process guarantees the proper brew temperature. The water will/can go North at any temperature. The pressure in the lower chamber is the determining factor.
You can fix the brew temperature problem by heating the water to about 190F before attaching the brew chamber to the top of the pot. I did this twice, and the coffee was significantly better. In fact, it was excellent.
Brew time is also a problem with this coffee maker. Regardless of whether you follow the manufacturer's recommendations, or use my 'heat first' method, the time the brew chamber is full (with hot water) is closer to two minutes than four. If you have a good grinder, you should be able to compensate with a finer grind and still get good results though.
Many people have adjusted brew time by tilting the unit and removing a seal. I decided to return the unit and forego the modification and tweaking.
If you are looking for the ultimate in coffee taste and are willing to put forth some effort, a regular vacuum pot would probably serve you best. You will have better control over both brew temperature and brew time. You can also obtain a regular vacpot for less money.
If you are looking for convenience and reasonably good coffee, I would look at one of the highly rated drip machines. While the coffee from this coffee maker is better than that from a good drip machine in some ways, it is less good in others. The coffee is soaked better, but at a lower temp. Since both this pot and good auto drip machines have brewing compromises, I don't see a compelling reason to put up with the cleanup hassles of this machine.
We only had the opportunity to try the timer function once, and we ended up with a very weak brew the next morning (not sure why). The possibility of inconsistent results coupled with the unexceptional coffee quality and messy cleanup made me realize that my girlfriend would probably bail out on me and buy a drip machine for the weekdays. So I would end up owning a $100 manual electricly heated vacpot. Once you write off the automatic abilities of the machine, it isn't nearly as attractive. I like to experiment, but neither of us has 15 minutes to monkey with the machine in the morning, and I wasn't excited about the "pot luck" coffee strength/flavor either.
I returned the machine. I've decided to stick with drip for the weekdays, but I'm considering an inexpensive vacpot for the weekends.