I’ve just put a Hylafax server in production, and now am in process of fixing little issues. Some things that have cropped up are:
Resizing legal faxes to letter
Fixing margin problems on printed faxes.

Both Some of these issues are related to the printer driver in CUPS. It works now with Foomatic/hpijs driver for the Laserjet 4 Plus. Also am now using fax2ps instead of tiff2ps.

Update: I’ve come to find that the margins of the printer can prevent the fax header from being printed on received faxes. To get around this printer limitation, I’ve specified a pagesize smaller than letter when invoking fax2ps.
i.e.)
prfax:~ # /usr/bin/fax2ps -S -H 10.8 -W 8.2 /var/spool/fax/recvq/fax000000072.tif | lpr

One of the difficult things is finding a good frontend for the windows clients. I’ve tried cypheus, jhylafax, and whfc. They all have their benefits and drawbacks. We settled for now on jyhlafax since it was less buggy than cypheus, and had legal page size support unlike whfc. Whfc was good for a lot of things including multiple customized cover pages. I may switch back over to WHFC since right now we have next to nil legal sized faxes going out. There are also web frontends that we could install. Here is a list of clients. The best one for a web frontend looks like AsterFax. I just have no time right now to test.