Strange; I can subscribe to user rss feeds in Newsblur.
I'm guessing Newsblur somehow rotates through all the users' collective RSS feeds in some manner to not trip the rate limit, which might explain why new posts don't show up immediately.
(Which is fine for me as a user; most of the reddit RSS feeds I subscribe to, I don't need to see immediately!)
The point is the feed is rate limited.
And you need one call per unique subreddit.
And Feedly's users collectively have more unique subreddits than the Reddit rate limit.