Vac pots (pretty much all vac pots) are cool, make good coffee, and are fun to watch.
It's easier to assemble the two halves than the gasketed Cory.
You can see the entire process a little better than gasket model.

It's easy to break.
The gasketless model doesn't always seal well, so "up" times and "down" time can vary significantly.
These buggers seem to be much more expensive than the gasketed models.

If you've never used a vac pot, you owe it to yourself to try one.  But probably not THIS one.  When you get everything just right, it works great.  But this particular model (without gasket) can be more unforgiving than alternatives in this space.

First the positives...  all vac pots are neat.  I haven't seen any exceptions yet.  And not many people are familiar with them, so they are a great novelty at a dinner party.  But most importantly, they really do make good coffee, in most cases much better than you would get from a high-end drip machine.  The Cory Gasketless is no exception.  Most of the time (more on that in a minute).  The machine is a nice size for a household with one or two coffee drinkers (three begins to push it).  It does a REASONABLY good job making small quanitities (4 six-ounce cups), but a better job with a full pot (six or seven six-ounce cups).  Because the machine is a stovetop unit, you have complete control over how long the coffee stays "north".  The Cory filter rod system is an advantage in that it's simple and works well, and doesn't rob the coffee of oils that a paper filter would.  And the major difference between the gasketed Corys is at the same time an advantage and a disadvantage - no gasket.  It's an advantage because the gaskets can dry-rot, and they can make mating the two vessels difficult (and prone to breaking - I've done it trying to press together the top and bottoms of gasketed Corys)).  You also get slightly better visibility since the gasket is not present to obstruct the view.  All of these attributes make the Cory gasketless a decent vac pot.

It's not without liabilities, however.  First, the general vac pot liabilities, common to most or all of them.  They are not super-easy to clean.  They are delicate (the glass ones).  And they are somewhat tempermental.  If the two halves are not mated well, you will experience frustration getting the water to "go north", or more likely, once north, it will spend an excessive amount of time there, failing to travel "south" rapidly.  The gasketless Cory, in my experience, is more prone to this problem than the gasketed model.  This is because the system relies on gravity to mate the top vessel to the bottom, as well as a little water between the two to create an air-tight seal.  Herein lies the problem, at least for me.  I like to pre-heat the water a bit before adding the top vessel (ulitmately it makes hotter coffee).  That tends to dry everything and make it difficult to get a great seal.  If you assemble it all ahead of time, you get a good enough seal, but cooler coffee.

So, in conclusion, I would say that the gasketless is a must-have addition to a vac pot collection, but not an everyday unit, or even the best performer in the collection.

This was a bit of a negative.  I bought mine on eBay, as most people do I'd imagine (mine's about 35 years old).  Now, I already owned several gasketed Corys, and paid $25-25 for each.  I bid on several gasketless units, and lost them at $50 (I really wanted to try one after breaking a pot trying to jam the gasket version together).  The one I finally won went for $70.  With the benefit of experience, I now believe that I paid too much given how well this machine performs.  But the bidding on these things seems to be tough, so brace yourself if you really want one.