After having a slot sit vacant for a week and a half (pointedly did not include any movies in my queue), I emailed CS to ask what was up. Shockingly, I got a reply within half a day even though it was Saturday.
The bad news is that apparently the availabilities they have listed on the site don't actually mean that your distribution center actually has any of the disc in question - if it says "available", that means they think they have availability nationally, but you can be sitting with an empty slot on your queue and multiple games listed as "available" and not get anything. CS recommends that you keep 10 titles that are "available" in your queue at all times to increase the chance that at least one will ACTUALLY be available. My mental response to that is that I'd be more willing to take my number 10 (or number 30, when you consider all of the delayed titles) choice if it didn't take two weeks to swap out a game.
The good news is that shipping speed seems to have improved after that snafu a few days back where all the games temporarily disappeared from queues. Suddenly, they've mailed out a pair of discs (neither of which has arrived yet, suggesting that perhaps they're mailing them from further away), both of which had previously been listed as short or long wait.
Overall, this service definitely has a long way to go until it gets to the point of working as advertised. That said, if the latest round of games arrive on schedule this week, I might still declare the service worthwhile in the short term. If I can get and beat four games per month (unambitious for a 2/out sub, but my expectations are low at this point) for $14, that's still probably the best deal I'm going to get on playing through those games.