The cross-server PF is a good start, but making /tell and the Friends list cross server as well would make getting together with friends a lot easier.

The Friends list will let you know which of your friends are online. Sending them a /tell will let them know that you're online. Your chances of getting together are a lot better once those two pieces of information are established than just putting up a Party Finder announcement saying "Hey, so-and-so, if you happen to be online and just happen to come here and read through all the PF announcements to find this, then let's get together."