I have tested couple of these code-inserters, but I like Sourcerer the most. While others can maybe include script file, with this component you can actually write the code inside ther article - a little like you would in normal HTLM-PHP-javascript coding.
I had this problem keeping variables alive from codeblock to codeblock, but it was fixed in less that 15 hours, including the night time! Awesome support!

I find the extension in it's work good, but the way license works might render it not working without notice. It will check your license against sitename and IP address. But since the IP address might change for many different reasons (ISP change, server change, webhotel change, malfunction..) it can suddeenly just stop working. And you need to open a ticket for that (simple email to support is not enough). That's why the extension is unstable regarding if it will work or not.

Anyway, this seems a good email tool, but be aware it might stop working without notice. Unless they change the licese to check only against domain name, which would be wise move.

I find this component very helpful when managing multiple Joomla!-based sites! It has allready most things needed.

Only thing that I missed is copying of separate components (instead of all, which is allready possible) from one site to another as easily as other parts.

Although I am sure this possibility will be included in future versions, so maybe it is allready included when you read this.. current version is 1.1.0