There are always room for improvements of the Experience Editor. Here are a few simple ones to fix.

Since Sitecore 8.1, field validation results are shown inline in text fields. This is quite useful for content editors, both for showing errors, but also to give soft errors, such as warnings or suggestions.

One can argue that all non-valid results from validators are errors, but I think it makes more sens to say “Show suggestion” instead of “Show error” next to a validation suggestion.

This can be fixed with a simple line change in
sitecore\shell\client\Sitecore\ExperienceEditor\ValidateFieldsUtil.js.
At about line 28, you’ll find the following row:
$(notification).append(DOMHelper.getNotificationOption(showErrorText, null, notificationId));
Just insert this line before it:
showErrorText = "Show " + validateFieldsUtil.getNotificationType(error);

If you’re managing sites with multiple languages, you might want to ask for a patch with reference number 55656. When editing a page, with components, in the Experience Editor, on a non-“en” language (assuming “en” is your Sitecore default UI language), validators are executed with the wrong context languages for components. Essentially, the validators are not being executed on the current language. Note that this error only applies to components, i.e items that are referenced from the current page being edited.

If you’re managing website where there are many items on the same level, you may also find it hard to use the navigation bar in the Experience Editor. Simply because there are no vertical scroll bars. Patch with reference number 85083 will fix this.