Can anyone recommend a good green screen keyer for use on a Mac Pro setup?

I've been using Serious Magic (now Adobe) Ultra, which generally works very well, with the reservation that it lacks full control, but the workflow (since this is a Windows app) is driving me nuts - I do everything else on the Mac Pro.

I've heard good things about Ultimatte Advantedge, but, apart from the fact that it's very, very expensive, they don't seem that close to releasing a version that runs on the Mac Pro.

The built in keyers in FC are usable, but also crude in comparison. (anyone heard whether FC6 has better keying technology?)

Thanks
Greg

I should add that I'd like to use the keyer within FC rather than exiting to another program.

Try DV Matte Pro from DV Garage, it's a plugin which will work right in FCP, they also have DV Matte Blast which works in real-time inside of Motion.
http://www.dvgarage.com/prod/prod.php?prod=dvmattefcp

I know this guy...and his software does a nice job and is quite easy to use.

http://www.oakstreetsoftware.com/gkey/

I also own shake and that works very well...I'm trying to convince him to write a plugin for shake based on his keyer.

Nate and Cole, thanks very much for the recommendations - I downloaded them and tried them out, but they don't seem to be able, for example, to handle hair as well as Ultra or Advantedge do. The price points are great though.