I am writing a longer UI entry, but just a quicky for this one:

Firstly, I feel that the Nokia N series is owned by "powerusers", who are more apt to tinker with their devices. Or is that too much of a generalization?

Secondly, something I noticed just yesterday: I use the fullscreen/normalscreen hardware button a lot when I'm fooling around with Flipclock (mainly because I noticed that the screen brightness in Insomniac Mode was much brighter than the minimum screen brightness setting of the 'Advanced backlight' program, but I wanted to point that out in a seperate entry altogether).
Since we are in 0.9.x beta release, FlipClock does not hang or freak out when you use the fullscreen/normalscreen button. This brought me to the following: you can use this button to bring FlipClock to a 'normal' screen setting, wherein you can see the 'normal' X exit button (at the top left of the screen).
If you know how to properly use the fullscreen/normalscreen button in order to use a program in fullscreen mode, you can also figure out that flipclock, which opens in fullscreen automatically, can be brought to a smaller version so you can find the X for exit.

My (new) suggestion is to remove the exit button on the screen and use the fullscreen/normalscreen hardware button in order to get to the X exit button.
You'll actually get an extra 'feature' when using this approach, because you can also minimize FlipClock if you want to use another program altogether. So instead of exiting the program everytime you want to do something else, you just minimize it.