Keep on the Shadowfell includes three large double-sided battle maps representing the locations of key encounters. Two of the three are recycled from the D&D Miniatures game.
This explains a lot. It explains why the "Kobold Lair" encounter as described doesn't match the included map.
As previously mentioned, in Keep the small town of Winterhaven is being plagued by kobold brigands. Lord Padraig duly dispatches the adventurers to stop the kobolds and slay their leader, a goblin named Irontooth.
The kobolds are laired in a cliffside cave, the entrance of which is hidden behind a waterfall. When the players arrive, they'll find the encounter split into two sections - a selection of guards outside the cave, and then the full kobold force inside.
The exterior encounter features several kobolds scattered along a narrow river just outside the cave. The river has only a couple of crossings, and dense forest on either side provides cover. It's generally a pretty okay battle, and most players I've come across enjoyed it despite the problems.
One of the problems is that the map depicts a giant glowing magical circle in the middle of the area. Players, no stranger to this sort of thing, tend to avoid it as though it were rabid, and often come up with strategies to "defuse it", or at least keep the kobolds from accessing its fell powers.
Of course, the circle is harmless. It's only there because the map has been recycled. The text in Keep on the Shadowfell passes it off as an ancient druidic circle that provides a minor attack bonus to anyone standing on it. What looks on the map like a gateway to another plane is really only a crumbling circle of menhirs. Really, it shouldn't have been there at all.
Also, the module claims that the only way into the kobold cave is by passing through the waterfall. Unfortunately, the map clearly shows two alternate tunnels to either side of the river. In this instance, it's more tactically interesting to ignore the module and play the map as drawn.
 4th Edition kobolds have two strengths - ranged attacks, and a "mob bonus" when multiple kobolds are in melee with the same enemy. Given this, are kobolds really well served by terrain dominated by tree cover and choke points?