I'm a long time SwiftKey user who actually paid to use the app. I've been very patient hoping some improvements would come. I love the keyboard, it's second to non that I have tried however, there are two main issues I have and they are both to do with the prediction bar.
First and most annoying issue I have is word prediction suffixes. It seems like 99% of the time the suffix to the word I'm typing is the wrong contextual suffix. This makes me have to type out the whole word instead of using your built in shortcut.
The second issue I have is spellchecker. It's basically useless if you've misspelled or mistyped the word early,within the first few letters. Particularly if you simply use the wrong vowel. I have a good vocabulary, but I've never been a particularly strong at spelling. It would be nice if misspelled words could be picked up and corrected even when the misspelling occurs within the first few letters.