I have been using KWYLL for a few months and it is an excellent piece of software. The GUI is so easy to navigate, it is not overcrowded and everything can be done with the mouse. The logic system is a bit daunting when you first look at it, but once you start to use it then it starts to become a lot clearer and logical!! The author is constantly updating KWYLL and works with the community he has created to further improve KWYLL by listening to users suggestions & ideas and implementing them where  possible .  The author also makes himself available to answer users questions about the use of KWYLL. There is no emulator connected directly to KWYLL, but the simulator built within program is something that makes debugging games very easy. Exporting to a .TAP file is only a few clicks and is exported very quickly and can then be loaded in to a Spectrum Emulator. Overall a lot of thought has gone into how the user interacts with the GUI and how a game is created.