Some pointers..
Remembering where the window was when last used is an absolute must. Using Windows' default positioning is strictly for amateurs!

So too, must remember things like column sorting order, last tab used, etc.
Modal dialogues like "foobar gives up, barfly wins one point" - avoid these like the plague. What if I want to have the program watch a match or series of matches (eg. a bot) for me but I'm away for 15 minutes, or what if I'm working in another program and just want Fibs in the background (perhaps I like to hear dice click and pieces get moved

)? Besides, having to click to say I've seen something that I may not care to see anyway is bad UI design. And having Windows chime its ALERT sound is a big

too. If I'm watching the game, I don't need to be alerted and if I'm away I don't want to rush back just to be told a game's ended!
loose.wav - The Internet's favourite spelling mistake! It's LOSE