I've tried pretty much every single keyboard out there and am using one not even on this poll's list - HTC IME mod, which i think is better than anything else out there right now - it absolutely flies without any hesitation at all.
You can find the .apk on XDA developers site. It's a modded version of the stock HTC keyboard but MUCH MUCH FASTER, plus a few tweaks (smiley button, swipe left to erase, etc).
I had been primarily using SwiftKeyX, but it's not as responsive as the HTC IME mod, especially if you add haptic feedback (which i've found really slows down most keyboards out there). I have HTC IME using only sounds for typing, not haptic, and it absolutely flies and is very accurate too.
You should look it up and compare... (and it's free)