I'm glad you provided the link to the propel page, it has confirmed what I always thought, it will NOT spped up you connection to the web. That is physically impossible. Their used to be a piece of software from Connectix that does EXACTLY what this so called accelerator does. It caches web pages in a more efficient manner, so that on you next visit to the site, it will use this better cache to load faster.
This will NOT improve download speed.
This will NOT improve connection speed.
This will NOT improve first time visits to web pages.
This WILL require you to reload pages multiple times, because the software will always want to pull the site from cache.
I say, take your extra $5 per month, and save for a G5