In the course of building my USB thumbdrive based ceph cluster I tried USB keys from three different manufacturers with a total of five different varieties of USB drives. Here are my impressions of them.
I have used 3 of the 8GB and 3 of the 32GB drives, both of the USB 3.0 Pen-Cap model (PBTech: 8GB | 32GB). One of the 8GB and 2 of the 32GB sticks failed (50%!). I have personal data on them so I don't want to return them for a refund in-case the failures are not total. I have had great feedback about these sticks from others and I did love the speed. However, they do run quite hot and perhaps the heavy IO loads of ceph melted them. They do have a blinky activity LED that is a gentle blue. The drives will stack on top of each other but are a too wide to stack side-by-side. However, stacking does increase the heat problem. The actual usage space is about 28-29GB this was low compared to competitors but the drives tended to be a bit cheaper.
The price probably makes them great for your briefcase/backpack but I wouldn't recommend them for high-usage.
I have 12 of the 8GB Cruzer Blade drives and one of the 32GB larger slide-cover Ultra3 thumb drives (PBTech: 8GB | 32GB). The Cruzer Blade style drives do not have an LED but thankfully I have had zero failures. The Cruzer Blade drives stack both horizontally and vertically in USB ports with a tiny bit of touching. The Ultra drive is too wide and tall to stack in USB ports but it does have a small blue activity LED. The Ultra3 would be my favourite USB drive for the briefcase/backpack because you get more usable storage than Apacer, the price is not much more and there's no cap to lose.
I have four of the 32GB JET USB DRIVEs (PBTech: 32GB). These are much too large to stack multiples in standard USB ports, though you might squeeze them in stacking vertically. I love the price, performance and reliability. The Strontium thumb drives have a red activity LED and they have never failed me. These are my favourite drives for Ceph -> when I want reliability. They do come with a cap - which I don't like for a briefcase/backpack drive though.
It should be said that the economics of running CEPH on USB flash drives doesn't add up. USB hard-drives give better price per GB and probably better performance too (particularly on my old laptops).
Read more about my Ceph Cluster.