Then, I opened a thread about existing games that could benefit, in terms of playability, if running at 7MHz (or more) at the spanish speccy.org forum...
http://foro.speccy.org/viewtopic.php?f=7&t=2842
...which led to some interesting games, namely: Fred, Kung-Fu Master, Match Day, After The War, any Freescape game, any flight simulator, Uchi Mata, Renegade, Target Renegade, Knight Lore, Heads over Heels, Batman, Football Manager, Carrier Command, Total Escape, Castle Master, Hard Driving, or Wec LeMans. I would add: the BASIC editor, when you are writting a very long line, press ENTER, and then a bug at the beginning of the line shows up. Using the left cursor to go up to the position of the bug is sloooooooooooow.