Back when I had a zx-81 (some three decades ago) one of the first things I did was order a replacement TI 99/4A keyboard. The wiring for most of the key-rows was the same, though the columns took a bit of reworking to build the correct keyboard matrix... thankfully the traces and solder points were all exposed on the bottom so rewiring was a snap with an x-acto and some bus wire. It was common practice on a lot of the old membrane and chiclet keyboard systems to adapt keyboards from other machines because they sucked so bad. The ONLY thing the old systems like the Spectrum had going for them were they were cheap... At a time where a level one basic Trash-80 model III would have set me back the cost of a new car, I was able to buy a ZX-80 kit for $199 USD.
Was always hard to say which was worse -- membrane keys or chiclet. It's why I laugh at the PATHETICALLY USELESS chiclet mac keyboards -- it sucked thirty years ago on the Coco, it sucked twenty-nine years ago on the Spectrum, it sucked twenty-seven years ago on the PC Jr., it sucked 26 years ago on the C=116, it sucked 25 years ago on the Enterprise 64... and frankly it sucks today on the netbooks that do it, and it sucks when Apple does it too.
But of course, Apple's reality distortion field prevents any of their rabid kool-aid drinking fanboys from actually noticing it...