After reading the reviews I thought this might be an alright little thing that has its problems but is otherwise easier than opening the flap and plugging the device in - it's not.
Inserting the charger is much more of a hassle than simply using a microUSB cable, the magnet often snaps to the side of the phone before the contacts are in place meaning it has to be very purposefully aimed and put in place - as much, if not more, of a hassle than opening the waterproof flap.
In regards to the comments saying it's fine on a table. The adapter has to be perpendicular to the contacts for the device to charge, the connection to the device is so weak than almost anything can dislodge it. The weight of the cable running off my desk to the wall charger is enough to often tug the adapter out of place, even the shape of the cable (after being coiled up during transport) can cause enough misalignment for the charger to not touch the contacts, resulting in me trying to flatten out the cable - considerably more of a problem than opening the flap.
Also more worryingly if the adapter is inserted reversed the device will crash, which is very easy to do as the connection is symmetrical and the adapter's orientation is only indicated by a small indent in the matte rubber finish (not glossy plastic as photographed), which is near impossible to see in low light.
The adapter is a nice idea, and is trying to make use of a feature that is very apparent on the Z1, but the fact that Sony have not released their own adapter, independent of their landscape dock, says a lot of what can be expected here. The magnetic charger was never designed to be used with manually inserted cable and is a total pain.