Just today, I went ahead and ordered the D-Link DIR-665. It was a tough decision, as both routers are very highly rated, but in the end, I found more positive reviews on the D-Link than I did on the Apple.
All the negative reviews regarding the Apple were the same... Endless dropped connections, machines being unable to connect and the firmware updates still failing to resolve this.
Whereas most of the negative reviews of the D-Link were very minor. Most dealt with the fact that it was based on 802.11n Draft 2.0, as are all the current n routers. There were very few negative reviews regarding real problems with the D-Link.
After seeing that the DIR-665 was an editor's choice in numerous publications, including PC Magazine, I decided it was a better choice than the AirPort Extreme. However, it does have a useless USB port that can't share a printer like the AE can.
I also bought a new Motorola Surfboard SB5120 cable modem to go along with the new router.