The original FASTmag created a unique flapless 30 round NATO magazine holding option, but as in all things, there was room for improvement. The latest Gen2 version clearly listened to user feedback and is a dramatic improvement.
The biggest issue most had was the size which is now similar to a typical nylon magazine pouch taking up 2 PALS channels and 3 rows. The PALS stabilizer extrusions at the top have been reduced to be as small as possible while still being functional. These stabilizers are also connected at an angle to cause the FASTmag to push the magazines slightly away from the body making them easier to grab. Retention options have been increased by having 3 grooves where a silicone band can be placed. The closer the band is placed to the opening, the stronger the grip. When I first saw this I noticed the band appeared to be a wrist bracelet with no text so I quickly amused myself by adding my own to not only create a stronger grip, but to style it up a dash. This grip increasing ability makes the up-side-down mount position even more viable. Many fear the up-side-down mount is asking for disaster, however my tests have found it reliable in most situations. Being able to grab a magazine from this position is very quick and comfortable. Be sure to view my test video to see the grip capabilities. That said, it isn't magic. When taking your vest off or while during long distance travel, go ahead and use the jump strap to secure your magazines. Although the grip is good on standard metal magazines, users have found that the grip is further enhanced with polymer magazines like the PMAG. The Lancer magazines also work, but one has to consider the built in ridge of the magazine and make sure it is not on the inner grip pads. If it is, some retention will be lost since the grip is mostly just on that ridge and not the whole magazine side. As for a small down-side, the pull tab end is now a plastic tab, I liked the original webbing version more since it was more to grab onto. The stabilizer pads are also very non forgiving PALS spec wise. If a channel is a little smaller than usual, the FASTmag will not mount properly and you will likely burn a good amount of elbow grease figuring that out.
Compared to other options out there, FASTmags only hold 1 magazine, but are quicker than flap magazines since there is no flap to get in your way. They are easier to use than shingle magazine pouches which can be a pain to reinsert magazines into and cannot be up-side-down mounted. Kydex pouches are the closest, however retention adjustment on them is global and cannot be reduced during mag extraction with a twist like on the FASTmag. Additionally, very few Kydex based designs come with a backup jump strap. If you are uninformed of the basics of the FASTmag, check out my Gen1 review. The Gen1 was pretty cool, but with all the improvements, my recommendation of the FASTmag Gen2 becomes that much stronger as a quick-reaction magazine pouch.
*NOTE: What I have to say here is opinion only. I try my best in testing, however I have not seen combat. Everyone should test their loadout configurations before deploying on a mission.