I tried a Spiked Chain with my taclord and just switched out of it for several reasons. First of all, the defense boost from a 1 handed weapon and shield comes in handy, even in a defender heavy group like ours. Attacks do get through, and you're probably not going to have a good Con. Hence few surges. Even with Durable, my warlord is often the first one to reach a critical level of surges - but we play many encounters per day.
Second, you need to be adjacent to enemies to flank. So providing a typically much needed bonus means not using the reach that you sacrificed some attack, defenses, and/or feats to get... Flanking usually seems sufficiently useful (you want every bonus to hit on those important encounter/daily powers you can arrange for your team) and easy to arrange that not going for it seems worse than wasting reach. So if you'll often end up adjacent for flanking (and possibly other feats), then why emphasize reach?
I'm not saying you shouldn't pack a reach weapon - they are very useful in certain situations like extremely tight quarters. But I don't think they're worth using as your primary weapon.