I guess the real question is:
Does darkness actually add anything to your game?
Without heavy modifications to the existing rules, I doubt it. The light rules as written are basically presented as a big screw to use against the PCs if they neglect to write "a light source" on their character sheet.
If you're going to go all out and actually work out where shadowy areas on a battlefield are, and actually play monsters as if they don't want to stumble about in the dark all the time, then I'd say feel free to enforce accurate usage of light sources along with it. I think such a system has the potential to add a lot to the game (ok, if you move over there with our light source, then I have concealment because I'm in the shadows from that statue, so I can hide!) but also a lot of complexity.
Using light in the Heroic tier adds a lot to atmosphere and gameplay, if done properly. Why were the alien films to exiting? Imagine how boring it would be if everyone had a massive "top down" view radius in the film...lol.
I think the reason WOTC put them in is that, with a table top, it can be a hassle working out the light. I sometimes use Maptool or FG2. Maptool in particular is amazing at doing lighting. If you are using such a tool I would suggest using light properly.
As for sunrods, they make stealth almost impossible, and also pre-warn any monsters of your approach. Lights visible from 1/2 mile way I thinkn in PHB. Or you can outright ban them for being lame (assuming your using maptool and running an underground adventure).
Here's a screenshot showing what Fog of War and dynamic light can add to the game.
Below is the first room in Rivenroar in FG2 with the party holding torches. The back wall is lit by the braziers, the adventurers can see up the steps and the back wall. Monsters are hiding since they heard the party smash open a door.
These pics are taken from maptool. This guy is equipped with a sun-rod. The PC version is first, the light lances into the room.
Here is the DM version. The light has tipped off anyone in the room of the advancing party.....
Also, I want to feel that players that chose dwarves/Drow can see better underground. Undead get a lot more interesting since they have darkvision, so you can have them drag PC into dark pits and corners and have their "way" with them.
All of this is really hard though if you are using normal paper dungeon tiles. I'd be interested to hear of any ideas anyone has. If you allow sunrods, I my opinion this actually makes it *harder* to work out light on paper; like I said I think they are there just to make the light rules "go away".