on LOAD has very specific uses, westor. There are times when you want to do something only on loading the script and not when mIRC starts. So, yes, it is very useful. For example, if I want to create a file with default values when a script is loaded, then I'd put that in the on LOAD event. I wouldn't want that in the on START event because it would create the file every time mIRC starts, overwriting the new values that may have been added.
As far as on START, think of that as starting (not loading) the script instead of just starting mIRC. If I wanted all my hash tables loaded when mIRC starts up, then I would also want them all loaded if a script is loaded after mIRC starts. Basically everything that I would put in the on START event should run when loading a script as well. Regardless if the script is started because mIRC is started or because the script is loaded, I'd still want the stuff to be done. Now, yes, you could duplicate everything and stick it into the on LOAD event as well as the on START event, but that's rather pointless. It's better to just have on START trigger for loading a script and starting mIRC.
If you have trouble with these events, then you're probably using them incorrectly. Use on START for everything that you want to happen when a script starts up (for any reason... loading or mIRC starting). Use on LOAD for everything that should only occur when the script is loaded, such as creating default settings. If you're using these for other things, you should probably consider whether or not there is a better way to do what you're doing.
Now, there may be a scenario where you want something to happen when mIRC starts, but not when a script loads, but that should be rare. If you think you have such an example, please post it here. Someone might suggest a better option.
