Since upgrading to version 0.4.4, I've been having problems where sometimes the Twitter-friendly link works, but sometimes it ends up redirecting from http://example.com/1234 to http://example.com/1234/ (with a slash at the end) and bringing up a no-posts-found error instead of redirecting to the original page.
It seems to be a conflict with WP Super Cache. If it's on or half-on, the first visit to the short URL works but subsequent ones don't. If it's off, the short URL works fine.
It's worth noting that I've been using both plugins for months, and it's only since upgrading Twitter Friendly Lings yesterday that I've seen the problem.