At one point, I disconnected the device (on purpose) and couldn't get it reconnected to the Lumia phone again. I'm still not sure what went wrong. I eventually got it all back up and running by reinstalling the app and pairing the device anew. That was fine for my single tag, but it would be annoying if I had to reset more than one.
Nokia does say that the system works better with Lumia phones using the Black OS version (which mytest device has).
Although the device on its own isn't very large, the Treasure Tag's dimensions made it too bulky for me to want to carry it around on my keychain or attach to my wallet, though it didn't affect my boat of a purse at all.
Pricing, availability, and should you buy it?
There are plenty of competing Bluetooth-tracking solutions out there, each which works with varying degrees of success. Some are smaller than this Treasure Tag, some have a sticker element, and some flash light in addition to buzzing and chiming.
In the US, you can find the Treasure Tag from Verizon for $30 and from other distributors, like Expansys, for closer to $40. In the UK, you can get it for about £19 from Amazon and £30 from Expansys. Expansys also sells it in Australia for $41.99.
I'm personally more interested in the smaller Nokia Treasure Tag Mini, which has the same height and width as the original, but is almost half the depth at 0.23 inch (5.8 mm) and a almost half as light, 0.21 ounce (6.2 grams). It doesn't have NFC pairing, battery life is a bit shorter at 120 days versus 180, and the optional loop knots through a notched window on the corner. None of these things scares me away.
The Mini will also sell for less; Nokia says it suggests the $17/€15 range, though I haven't seen official pricing from distributors yet.
Overall, I like the Treasure Tag just fine, including its aesthetic, but if you're really set on keeping an eye on your valuables, I'd shop around for other devices that are smaller, light up, and cost about the same.