I've left a longish review of this plug-in that mentions two other issues or suggestions - better OAuth implementation, more settings or output-formatting options - but I've run into a third, more serious problem with output formatting that I suspect make have something to do with the variations on "make_clickable."
In short, in the twitter digest output, certain URLs, especially picture URLS, are getting cut off and made dysfunctional. For example, an url that in the original tweet, on Twitter, is "http://t.co/4W4rysT0Iw" is rendered as "http://t.co.../" I've noticed another blog uses Twitter Digest that also occasionally has URL-rendering problems, though not with as great a frequency as on my results so far.
I notice comment on line 364 of twitter-digest.php, in the function ws_make_clickable: " // make_clickable doesn't handle (url) very well, so we'll chuck some spaces in." Doesn't give me a whole lot of confidence in what follows, and I wonder if it's the problem. So, it looks like I'll have to research preg_replace and REGEX to see what the intention was and whether this is, indeed, the source of the problem, unless the developer is monitoring this thread actively and can provide a better suggestions (this could be completely of base, for all I know at this point).
I have some other suggestions for further developing the plug-in, but I'll leave things at this for now, and maybe leave a note