Anyone who tends to use multiple thumbdrives and switch between them a lot, *run* to get this. I registered USB Safely Remove a year ago almost to the day, and it has been fantastic. Note that with a standard (paid) registration you get lifetime updates, so this offer is a bit of a tease, as upgrades are excluded. You're still getting a fully-functional app for free, and I haven't had any problems at all with the current version.
I originally registered for version 4.0 beta, and a year later USB SR is at 4.1, so it's quite mature and stable (i.e, no rushed new releases every couple of months).
Tip of the day: try Win+Delete for the main hotkey, it's very convenient (ymmv, depending on the placement of the Delete key on your keyboard). It has become a second nature to press this, and hit Enter to disconnet a drive. USB SR you can also show any other USB-connected devices and their status, and lets you assign permanent letters to particular drives. One other neat feature is to reconnect a drive that you've just disconnected by mistake - no need to physically remove the thumbdrive and plug it in again.
It's one of those apps that run invisibly so that you can almost forget you have them, until you sit at a computer that does not. I really recommend this one, and those who've been reading my DC posts know I rarely gush about software (unless it's TotalCommander, of course, which can do no wrong