I haven't done the live-usb yet so I can't comment on it, but I do know this...often times too many moving parts can spoil a good thing.
I am all for choice, but with every choice comes a cost. I would suspect that the majority of users downloading this product ; are above beginner but below expert. Hence the need to KISS (Keep It Simply Simple).
Another thing to consider is how often this tool will be used by the average user. Surely many of us have it burnt to cd and it is as a much a part of our computing tool set as a screw driver or hammer in the shed. BUT, most people will only use it one or two times to get what they want, then not use it again. The question then is, are your advanced users really in need of two ways to access the tool set.
I will try to use the isolinux soon so I can comment upon it.
In response to "So what?", There is an story that when Thomas Edison invented the light bulb, it was deep in the night hours when it worked correctly. He went and woke up his wife to show her, she sleepily stated. "Great honey, now turn the light off and come to bed".
Whether or not that is a true story, the point is similar. Most people may not even know the difference when Gparted is upgraded, most of us will keep on using it for our specific purpose. No matter, you who have upgraded it will still have the reward of knowing all that this product can do. That is priceless!