Last night Apple released a firmware update for Time Capsule, AirPort Extreme, and AirPort Express Base Station with 802.11n. Here are the fixes:
Fixes some problems with extending and maintaining connectivity with extended networks
Fixes an issue with clients that enable 802.11 "Power Save"
Fixes connectivity issues with some third-party devices
Fixes an issue when the base station is configured for PPPoE
Fixes some Back To My Mac issues with connectivity and support for third-party routers
All of those sound like issues that could affect quite a few people -- especially those with (gasp!) "third-party" devices. I've certainly had issues with Back To My Mac using a Netgear router, so we'll see if this helps. In any event, firmware updates are recommended especially if you've had any of the above symptoms.