Things it would be nice to see in 5.1:
Support for DDNS services when running as a server as well as in gateway mode. I use e-smith at home, behind a Netopia box that NATs my network (I only connect the minimum number of ports - 80, 443, and 25). Since it's not a gateway, I have no direct access to DDNS services - and AFAIK, e-smith's DDNS service can't detect when the IP address is on the other side of a firewall, anyhow.
In the same vein, I'd like to see ZoneEdit be one of the supported DDNS providers I've had a very good experience with them in the 9 months I've used them for DNS hosting.