My Zenclass Review (Updated twice):

The ZenClass Nirvana Seat-Back Organizer and Travel Tote is a remarkable carry-on bag for airplane flights. (It's also handy in cars, on strollers and on changing tables!) I believe it's not perfect, but it's so wonderful that I look forward to discovering how to take advantage of all it offers. Here's a wonderful video to show its versatility.

The ZenClass bag zips up to form a small, light carry-on bag, about 8 by 12 inches and thin. (You'll probably keep it in your fullsize carry-on. Or you can wear it on your belt or body, in several different ways.) When you get on the plane, you unzip it and hang it over the tray that comes with your seat. The ZenClass bag has an ingenious flap for this purpose. You lock the tray in its closed position, and now all the contents of the ZenClass bag are available to you. There are three goodsize zip pockets, several see-through mesh pockets, and various special purpose holders (e.g., for a passport, for a ticket, for a pen). Depending on how you load it, you now have everything you need -- even a paperback book -- within reach for your whole flight. (You can even pop your laptop into the open bag.)

Beverage service does not require you to put your tray down; the ZenClass bag has a cupholder. When your meal comes, make sure that most of the ZenClass bag's contents are in its (closed) zip pockets. Then open the tray to eat, and the ZenClass bag will hide under the tray until you're done with your food.

I tried the ZenClass bag out on two eleven-hour flghts, and I never needed anything that was out of reach: pills, reading material, snacks, you name it.

The ZenClass bag doesn't interfere with the seat pocket below your tray, so you can fill that up too. It costs $39.99 plus shipping. I've found a few negative aspects of the ZenClass bag; perhaps some of these comments reflect my lack of experience with it:

-1: The ZenClass bag doesn't fully close when not in use. It zips three-quarters closed; the top side is "auto-closed" by magnets. I believe it's possible for small things to fall out of the top, so when the ZenClass bag is closed, I make sure that almost all its contents are zipped up in its inner pockets; a slight nuisance.

-2: It's hard to get the zipper moving when you want to close the ZenClass bag. And it gets harder, the more you fill it.

-3: Although the ZenClass bag has neat see-though pockets, your stuff will spend a lot of time zipped up out of sigtht. I think it's necessary to review what I've stuffed in all those pockets from time to time, to make sure I know what I've got.

-4: If you use a laptop on a flight, you're going to keep the tray down a lot. You'll have to get the laptop out of the way, each time you need the ZenClass bag.

Update:
Brent Hollowell (of ZenClass) wrote the following:
All of our new product has YKK zippers - the highest quality brand name zippers available. UPDATE: {I talked to Brent about the magnetic top, and found that no one has complained that they lost anything out of the top of the ZenClass bag. Thus the magnetic top appears to work just fine, although there are people like me who worry that something might fall out, when the bag is not in its normal vertical position. The magnetic top allows easy access to items in the top of the bag: passports, tickets, etc.}

In the "tray table down" position, in order to use your laptop and the organizer at the same time, try this: In the long zippered pocket that spans the entire bag, lay something fairly rigid/structured (like a couple of magazines, newspaper, book, notebook or even a laptop when not in use) across the entire inside of the pocket, horizontally, so that it spans the mid-point or folding part of the bag. This will give the bag a solid structure in the open position. You can then rest the entire unit on the metal tray table "arms"that hold the table in place (these are parallel to the floor on most current aircraft equipment).The back lip of the tray should meet the bottom edge of the organizer and hold it fairly well in position so that you can use the tray table.

It's not the most elegant solution, but unless it's insanely turbulent (or you're flying on an aircraft with the older tray tables) then you should be OK to use it in this manner as well. We did not design it for this mode, but we are working on a (hopefully) simple solution that will make it easily usable in both modes... trying to do it simply without adding quite a bit of cost, so we want to be deliberate about how we solve this one!