I find that the winform tool tips behave very erratically. They seem to randomly decide to do nothing, show up or disappear when I perform the same hovering/clicking/etc actions.
Is there some pattern that I'm missing? Do I just not understand the UI technique to bring up a tooltip? Is this a common problem? Do people actually expect tool tips to work this way?
Tooltips display automatically. That's a bit of a problem, the native Windows control has counter-measures in place to avoid displaying tips too often, potentially wearing out the user with info that has been shown frequently enough. Not exactly sure how that rate limiting is implemented, accumulated time is a factor (like 60 seconds), possibly also the number of times it was displayed.
The SDK docs do not document the implementation details. There is also no message available to forcibly reset the rate limiter. I do think that passing another control in the Show() method resets it.
All and all, it does mean that the ToolTip control is really only suitable to act as a traditional tool tip. It doesn't work well as a 'dynamic label'. which is your alternative, a Label control with BackColor = Info. Albeit it not quite the same because you cannot easily make it a top-level window.