Originally, I purchased a narrow-neck Silex vacpot, having heard that the seal created by the small neck would be tighter and would thus lead to better trip North and suckdown. Neither of these have been true in my case. My biggest problem with the Silex was that the tube did not extend far enough into the carafe, leaving way too much water in the lower section, diluting the finished brew.
My second vacpot, a Cory Large Gasket marked DRU3 and DRL, solves this problem. Furthermore, it is much easier to pour the preheated water into the lower sectioni with the large opening. First, I set some water to boil. Once I hear the whistle, I turn off the stove, grind my coffee, insert my "NEW Cory Rod" (more on this later) into the upper chamber, pour the medium ground coffee above the filter, and finally seat the upper onto the lower by inserting it at an angle and then pushing firmly so that it evenly seals. The hot water immediately begins to rise into the upper. I then place it over a medium-low flame. The trip north is pretty slow on my device, taking about 60-75 seconds total. As soon as all the water (all, that is, that is going to make the trip) has risen, I turn down the stove to its lowest level. I let it bubble for about 2-3 minutes, stirring once with a long spoon (being VERY careful not to bump the top of the Cory Rod). Without stirring, there would be much unsaturated coffee even with the bubbling. Finally, I turn off the heat and place it on a dry towel. The suckdown starts almost immediately. Strangely, I have had some nearly perfect suckdowns (less than 60 seconds) and others that take 2-3 minutes. Either way, though, the grounds in the top section have been sucked dry and the cup quality seems to be the same. I'm not sure why this varies so much - it is the same grind. Perhaps the quality of the gasket seal I create is somewhat out of my hands...
So how does it taste? Great. It truly creates the best drip/infusion coffee in the world. The only thing that comes close in my mind is a chemex with a muslin cloth Coffee Sock filter, but the vacpot is a bit cleaner and the flavors are a bit more heightened. Now you're probably wondering what I mean by a "clean cup". I have read countless times that the Cory Rod glass filter creates a great cup of coffee but that the drawback is the tangible amount of sediment that it leaves in the cup. I sometimes wonder if I'm doing something totally different than these people. I get ALMOST NO SEDIMENT. AND, I'm using a crappy whirly blade grinder set to medium (so I know that there is lots of powder created). Nonetheless, the "New Cory Rod" filters it all out. Held up to the light, it appears only a tiny bit more cloudy than the brew created by thick Chemex paper filters. I am very pleased by this cup quality, but wonder why the reviews of the Cory Rod are so mixed. I suspect it is because some people are using an older rod labelled "Cory Rod Filter". This original Cory rod was reengineered specifically for coffee creeating the "New Cory Rod". Believe me, the latter is awesome, and if you purchase one off of eBay, be sure that you are getting the "New" version.
Overall, I love the Cory large gasket. The cup can be a bit inconsistent, though, but this is probably due to my learning curve. Though I'm using it every day now, it may be a brewing method that I have to eventually relegate to the weekends - due to the time involved and the worry that I will break the non-Pyrex glass that my Cory is made of. Furthermore, due to the varied suckdown time (60-180 seconds) this is not a very theatrical way to impress your friends. Unless, that is, your friends are impressed by a truly unmatched cup of joe.