I've decided to get the Imperial Heralds that I know to have RPG content (and Clan War content as well, actually). I've just received the first one from eBay and while it confirmed that it wasn't worth a subscription it's actually quite ok.
The first Imperial Herald with RPG content which is I believe the seventh published, which is a small FAQ Errata, including movement rules, and a complete adventure called alone in the Dark.
Alone in the Dark is in fact a rather competent horror romp. It lack a bit in that doesn't suggest how to involve the players, nor does it give any advice on running it, but I suppose it is understandable considering it's published in a periodic newsletter with limited page count and mostly devoted to a CCG.
Taking that into account I suppose it's greater flaw is that, as one of the first published L5R adventures, the Horror genre in an awkward choice. At this point in the line there wasn't much advice on running horror L5R and as stated above, there is no advice in the adventure for it, making it less useful for a GM with good grasp on horror gaming.