The Cherry Cymotion Expert is the best mid range keyboard Cherry has produced. Unfortunately it is no longer in production, so if you can find one, buy it.
The Cymotion is comfortable to use, with firm, responsive keys and is built like the proverbial brick outhouse. My present keyboard has withstood 6 years of punishment and is still going strong.
The models Cherry has replaced this with (like the Stream XT) are not a fraction as comfortable, look ugly to me and worst, are disappointingly flimsy. If you can't find a Cymotion, buy one of Cherry's basic £10 models, they are far better than the present mid-range models. Or buy one of their programmer's keyboards.