Admittedly you can buy cheap and (usually nasty) plastic Bluetooth keyboards for £20 or so, but this all-cloth and rubber Microsoft offering is just so much nicer in the pocket and in the hand, plus it'll probably last longer too.
From the intro to my original review:
Bluetooth keyboards have gone into and out of fashion over the years, but they're definitely in vogue at the moment, thanks to the use of tablets and 'phablet'-style large-screened smartphones, where a wireless full size keyboard can turn the device into a mini-laptop.
The materials are one of the biggest USPs:
The Universal Foldable Keyboard itself is constructed from a fold of heavy duty material, which is nicely textured and smells like leather, though I'm no expert here - the blurb on the Microsoft web site does emphasise that it's water-repellent, as indeed are the key mechanisms, so an accidental beer spill may not be the end of the world. The edges are formed sharply, making for a good grip and protecting the edges of the main material. The sole port is microUSB in, for charging, at the top right of the keyboard. Battery life isn't quoted anywhere, but from my tests it's in the region of eight hours of use on a charge, whcih should be more than enough for anyone, plus it's trivial to recharge it.
Things are lovely on the inside too, dominated by the 'gap' in the middle, which may or may not prove a sticking point for you:
Opened out, the premium feel continues, with a well made keys arranged in two panels (either side of the fabric hinge, which presumably also hides a ribbon cable). Key travel is only a couple of millimetres, but the feel is terrific, akin to that on a netBook... In addition to the usual alphanumeric and control keys, there's a 'Home' key, plus volume and media controls, lock and search controls. These work with most modern (read Bluetooth 4 and above-compatible) operating systems, though again there's a caveat below.
Love it or hate it, the gap is there. In fairness, after an hour or two on the keyboard I did start to get used to it. No longer put off by an outrageous price, I wanted to like this accessory a heck of a lot more than when it was £99...
The concerns in the original review have mainly melted away - Windows 10 Mobile's Bluetooth stack and profile compatibility is now pretty good and almost all the function and media controls worked on my Fast ring test Lumia. Plus that £99 insanity is now £39.99 and reasonable.
Moving the Microsoft Universal Foldable Keyboard well into my 'recommended accessories' list. Go grab it on Amazon UK or a local outlet to you, just be aware that the new reference price is £40 or so!