Getting onto the spill-resistant keyboard, it gives the impression of being the most compact Logitech model we've had through here in a while, thanks to the incredibly narrow space around the keys and lack of media and shortcut buttons above or to the sides of them. In fact, it's about six centimetres shorter than the Wave, although the silver-blue wrist-rest extends outward by about half a centimetre on each side making the total width 43.5cm. Overall, the look of matte black typing area and surround with the distinct and broader wrist-rest makes for an unusual but attractive look.
Key layout is very compact. Logitech's signature right-Fn button makes a welcome return to give secondary functions to the F1-12 keys. Just above the number pad are a handy calculator shortcut button and a battery indicator whose secondary function is as a power button. As mentioned, multimedia and shortcut buttons (which include zoom, volume and play/pause/skip controls) aren't arranged along the top or sides. Instead these are cleverly integrated onto a narrow glossy strip between the key area and wrist-rest.
In terms of feedback, the S520 keyboard is a pleasure to use. The low-profile keys feel a bit lighter than on more expensive models, but offer a good amount of travel and very positive response, with that definitive feel essential for vast amounts of typing. Their matte texture is also pleasant and prevents slippage. The keyboard is not too noisy either, with the space-bar being the only moderate offender.
The wrist-rest is quite comfortable, though it doesn't hold a candle to the padded one on the Wave. On the other hand, I actually prefer the way the keys feel and their shallow profile to the Wave's deep keys with their soft feedback. As with all modern Logitech keyboards, there are two degrees of tilt available thanks to the twin pairs of legs of different lengths on the keyboard's bottom.
When all's said and done, would I rather use the Wave? Well yes, thanks to the better wrist-rest, dongle and far superior mouse. But not everyone will want to pay the £40 premium this demands. As budget options go, you can't really go far wrong with the Logitech's S520 Cordless Desktop for under £33, especially since a similarly-priced option from Microsoft will get you 'antiquated' optical technology.
If you want the cheapest wireless keyboard set out there that'll still look decent without causing RSI after a few minutes, the Logitech Cordless Desktop S520 is definitely worth considering.