Although Wagaya no Oinari-sama hasn't always worked for me, this particular story arc covering Shiro/Byakki seems to be the best yet, drawing me into this series better than any of the plot points that have preceeded it.
It is perhaps this factor that let me to be a little more disappointed with episode seventeen, as it seems to get mired down a little in an instalment where not a great deal happens in all honesty. We do find out a number of important things, such as just who the odd pairing who have been following Byakki around are, and also what Byakki's modus operandi is, but a lot of this is covered in reasonably short order, leaving us with an episode largely around Tooru being chased around and bumping into Mubyou (or rather, her look-alike assistant) and poor old Sakura, who always seems to get dragged into these things.
Thus, there isn't a great deal to say about this episode - It pulls together most of the major characters from the series so far (albeit in a slightly clumsy way) but mainly seems to be a warm-up act for the episodes to follow where doubtless things will get more heated. This isn't a bad move in itself, so I can forgive it for being meticulous in its build-up, but unfortunately it didn't make for the most entertaining of episodes in the process.