I have used Notepad extensively but it is not without problems. The most obvious issue is the file size limitations which prevents it from opening larger files, such as detailed logfiles. There is one strange but mostly harmless bug that sometimes causes it to jump back several characters after you save. Sometimes it also inserts blank glyphs (boxes which look roughly like two square brackets []) but I’m not sure why. I’m sure if you started throwing lots of different text Encodings and binary files at Notepad you could get it to fail in various ways.

P.S. The lime Green text on white background hurts my eyes. Light grey on White is asking for eye strain too.