It arrived last night, and I've had a short play with it today. I'm quite happy with it. It gives me a lot more info than I get from my smartphone app, and it hooks up to the GPS a LOT better, meaning I'm not sitting waiting for a few minutes before I can set off.
The facility to use it as a live speedo is nice, and the bike mounts it comes with are both simple and effective to fit it to the frame. Its waterproof to IPX7 so no problems about a torrential downpour.
Now the niggles:
The rear rubber housing for the USB hub has fallen off and is lost already after one ride. I don't know if this will affect the waterproofness. Email sent to Holux. If it doesn't, its no big deal.
The default setting for cycling seems to take GPS logs every five seconds. (The live reading updates much faster, I'm talking about what it actually records to the log) This isn't quiet fast enough IMO - I've got a couple of fast corners where the track sows me cutting it, and hell, I want every mile taken into account! Its again not a big issue as you can alter the interval/distance it logs at, so I've upped it to 2 seconds to see how that goes.