The concept of RSS itself, like any other piece of technology, is not something users should understand directly. What RSS lacks is a simple, friendly concept to act as its public face. The ways people have explained RSS in the past have been daunting, unappealing, or inappropriate for the web.
"Subscription" is the most common term used, probably because it is a reference to the underlying technology (publish/subscribe) and to a vaguely similar concept in userland (subscribing to a publication.) But subscription is not a good metaphor. Subscriptions do not lessen your commitment; they increase it. Having a bunch of magazine subscriptions is a burden! They fill up your mailbox and clutter up your apartment. A "subscribe" button scares people away because it evokes a much more consequential decision; the user wonders if it is worthwhile to commit to this burden. And of course subscription is not the only way to use RSS.
What web sites and browsers need to do is simply SAY in their UI what the RSS features do, without saying "RSS" and without trying to train users to recognize the RSS symbol.
I am not a UI designer, but I think the word we're looking for is "updates." Buttons should say:
"Show me recent updates to this site"
"Show me future updates to this topic"
"I want to see future updates to this site"
The button to show your RSS feeds should say "Updates" and should have a tooltip saying "Updates to your web sites."
To help people discover this functionality, I think it would be great for browsers to check for RSS feeds on the sites a user goes to frequently and work that into the UI somehow. When you open Chrome and see thumbnails of your favorite sites, each thumbnail might have a button saying, "Recent updates...."
And there's one simple feature that people would easily figure out and would actually use. When you're on a site that has an RSS feed, there could be a little pop-over button in a corner (like the button added by Feedly's Firefox plugin) that you can click to see a list of recent updates to a site. It's a simple feature, some people would figure it out for themselves, and anyone could grasp how it worked after seeing it used once or twice. It would put pressure on websites to provide good RSS feeds, because they would know many users were checking them. Here's a tip: put the words "Recent updates" on the button.
tl;dr Don't say RSS, don't use a symbol, don't say "subscribe" or "subscription," just use the word "updates" and say what you mean.