In Safari windows at least, it's Opt-Escape. It should work in most Cocoa applications. It won't work in non-Cocoa apps like Office 04. I always forget about it. It's actually a very nice feature for when I'm using some more obscure word that's hard to spell....I might be wrong but IIRC then when typing you can press escape and it will fill out the rest of the word for you, not very quick but the germ of the idea is already present.
You can pretty easily train (assuming you don't have any motor or neuromotor problems) to get at least up to around 80WPM... using predictive text requires you to interact back and forth much more than touch typing. Do you really think that you'll be able to do interactive faster than that? The only thing I've ever really heard of that's faster than good touch typing is voice recognition, and it has its own problems.i don't need a typing application because I cannot type, I require it because i have an activity where typing at high speed with accuracy would be needed.