I am a professional software developper -- I'm VERY picky about 1) screen 2) keyboard and 3) chair. So When I say this is the best keyboard you can buy, and it's £9.99, that should put some emphasis on the review.
I discovered this keyboard by chance, as it was shipped as standard with some Atom mini PC ASUS or ACER -- I immediately realised they were pretty good, and it took a while to track it back to this (I assume) manufacturer.
So, first, lets talk about the num keypad. Been typing for 30+ years, I /never/ used a num keypad. I'm not a beancounter, to me, it's just a waste of space. Also, it increases the distance you need to move your (right, if you're not a lefty) hand from keyboard to mouse and back, increasing muscle/wrist strain. So basically, num keypads are to be considered Evil. Unless you are a lefty, or a beancounter (not sure what is worse! </joke>)
Second, you will have a lot of people raving about their M-type keyboard, that requires about two fingers the press the keys, and make a noise that will irritate the people next door. Needless to say, that lovely hard vibration that is perhaps satisfying on some level also translates to your finger's articulations, in a similar process as doing some running without the right shoes on hard concrete. So if you have any sense, forget it.
Third, there is a 'wireless' thing. I'm (also) a mac user; and you get nagged incessantly about having to recharge your batteries. Hold on, I'm on a DESK here, I have a 7 port hub here, why, exactly, do I need flippin batteries in my keyboard? It went far enough that I actually ripped my Apple fancy "Magic Trackpad" apart and installed a Cable ( see https://plus.google.com/+MichelPollet/posts/W13aNkca8Qx if you don't beleive this) to get rid of the problem.
So it comes down to this keyboard here; it has very nice action (not marshmallow, but not M-type) -- it has ALL THE KEYS (including Pgup/down/home/del etc) it has a full complement of function keys, has 2 controls, 2 shifts and a set of other useless functions when you press the 'FN' key. Key spacing is just about perfect, plastic is nice and durable, it's very easy to clean (even the white one) -- try using a kitchen towel with some Naphta (aka lighter fuel) -- it'll get spotless in no time.
It works perfectly well on the mac, the 'windows' key acts as 'command' and 'alt' as 'option'; it works perfectly well on my linux boxes too.
Seriously, I can't think of anything better than this; I use one of these on every single machine I own, and even brought one at the office and tossed the provided Dhell into a drawer. This a gem; stock up!