Today, I noticed that when signing into bugs.webkit.org I ended up having to manually tap then Log in button because I faithfully filled out the login form in order (top-to-bottom): email, password, then unchecked the bound session to IP address checkbox. The last action, unchecking the checkbox, caused the password field to become defocused and hence pressing the return key no longer would submit the form and log me in.
We should find a way to improve this experience as it significantly effects a person flow. One idea is to keep the keyboard on-screen when switching from a text field to a non-text field control (maybe even keep it on screen if we tab-focused via full keyboard access to a non-text field control). For all other cases, we would do what we do now and not show the keyboard.