Funnily enough, I've used Microsoft Ergonomic 4000 for a decade, and its split design forced me to learn touch typing because I've always tried to cross that gap and landed in the split.

Also after getting used to it, it was one of the most reliable and comfortable keyboards that I've ever used. However, I've eventually wore it down and its keys started to get heavier. So, I moved to G710+, and I'm very happy now.