I liked this episode.

Did anyone else think maybe Tsunade only told them it was B rank so Naruto wouldn't bother her about giving them dumb missions?
Another explanation could be that its higher rank because Kakashi is not with them. Perhaps it would normally have been a C-rank.

About why they couldn't catch up to the guy. If I remember correctly, somebody during the Chuunin exam said that Sasuke takes up a whole lot of stamina maintining his "Lee" speed. Since he's a marathon runner, I would assume this guy can keep up that speed for a really, really long time. Also, since his training is focused on speed solely, not even fighting (from what we've seen), it's reasonable to say that he can go as fast as Sasuke and Lee. So, Sasuke might be able to keep up with him, but in the long run, the new guy would outrun him.

I think that if/when this links up with Ibiki, it might get interesting.