When I type a word with no errors, and make sense in context, sometimes it will be corrected to another word that it thinks will be more appropriate. I would like an option to only correct simple typos, and not alter correct words entirely.

the ability to customise where you want your own punctuation keys within the main keyboard page would be a good idea :)

Simply the option to disable next word prediction and only keep auto correction suggestions would be nice. Also, having more than 3 suggestions at a time would go a long way in not having to waste time retyping things.

The buttons are very small and quite difficult to see or hit. Any ways to improve the layout? might want to explore on that

Include text expansion options like found on iOs

More sound options which can be borrowed from windows phone or ios

Swype does this brilliantly and I miss it. I often want to have a word uppercase mid sentence then find myself fumbling to correct it later. If Flow had a method similar that would be brilliant!

I find the "flow trail" ridged and jerky. Ironic for a program called "Flow".
Also while I do like the color and the progressing change of color the older the trail is, the three lines that make up the trail make it look like a bad felt tip pen. It should just be a solid line.

perché solo tre parole suggerite o piuttosto fare uno scorrimento orizzontale della barra con altre parole suggerite?

The idea is that the typing language is detected from the first words typed and then to predict in that language. The current used language should be displayed, and the user would be able to switch to any other installed language. A setting could be added to choose between auto detection and pre defining the default language.
This way the other dictionaries would be active only when needed. The occasional word in another language could be chosen after quick switching the current language, and the suggestions would be refreshed to match the new language.

When you're filling out forms, when you click the e-mail field, the SwiftKey keyboard changes: predictions turn off and swype turns off. That means, you have to type in your email letter-by-letter each and every time.

Suggestion: The keyboard should NOT change. It should remember email addresses and show up in predictions. There is no need to change the keyboard and show the BIG "@" sign. It is already present in the default/primary view in the "a" key.

I want to use Flow in portrait mode but not in landscape mode, where I'd rather use gestures like swipe delete Nd hide keyboard through swiping...

I use LastPass for passwords and the stock KB will allow long press space bar to quickly change input rather than going to the Notification bar or settings. LastPass will also let me switch keyboards by long pressing on the LastPass button. This makes it easy to switch between Keyboards.