Jetpack is the future. Give the old school add-ons up, it's over. Because sooner or later everything will be possible with some CommonJS style module, which would mean you'd be a fool to ignore these modules.
At the moment, I see normal restartless add-ons as those that write their own bootstrap.js file, which is a method I've been trying to help people learn to do with this series, because I felt it would be a stepping stone to converting existing old school add-ons to Jetpacks which I needed, and that other developers might need as well. Now, I can't explain why very well, but I feel that there is a freedom writing the bootstrap yourself which is very nice, and although it requires me to think about how to cleanup my code a lot more, that's something I needed.
There are serious drawbacks to building Jetpacks I think as well. Such as the file size of Jetpacks, a simple add-on which only uses a couple of the built-in modules is actually shipped with every module built-in to the add-on sdk, which means that anything you build will be at least ~250kb no matter what it does. Now that just sucks for desktop users, but for mobile users it really sucks.
Now though, I'm starting to write some common includes for my restartless add-ons, and those which I contribute to, which I'd like to share, and I'm starting to see Jetpack modules/packages being written that I want to use in my restartless add-ons. So I thought "it'd be nice to have a require() method for bootstrap.js", so I wrote a simple one:
If you copy & paste this code into your bootstrap.js file somewhere near the top of the file then you will have a require() method which will look in your add-on's "packages" folder for a ".js" file with the name you provide, if a module is not found there then the name is assumed to be a relative url.
With that you can start writing CommonJS modules which can be used by Jetpacks and even NodeJS and the like, as well as for your lean mean restartless add-ons. You can even start using Jetpack modules and other CommonJS style modules in your restartless add-on as well!
As always you can checkout Restartless Restart as a example.