I've been running DD for as long as I can remember, and I'm very, very happy with it. Absolutely no problems with installation, configuration or day-to-day operations. YMMV.
I tend to end up using my wireless gear in dumb WAP mode. This is usually precipitated by wanting full specific control of my firewall/NAT configuration, full control of DHCP and my public IP attached to something with storage. That said, the interface and feature set of DD is nice enough that I'll probably give it a shot next time I flatten my home network, and DD is probably powerful enough that it will stick for a while.
* tunneling: I work mobile and tunnel everything through ssh and/or openvpn using my primary home router.
* signal boost: I can't get reception everywhere I need to without it
* dynamic dns updating: it keeps my dyndns stuff updated automatically
* Wireless bridge: for example, the xbox wireless adapter is $100, but I just took an wrt54g router (about $50) set it up as a bridge and use that. Similar situation for older devices in the kitchen that can't use the wireless on their own.