I have indeed tried without succes (was going to post but have to find a way to include my xorg.conf and log files).
With the vesa driver, I actually get a graphic console attempting to open, but it doesn't display correctly (so I have to ctrl-alt-f1 and ctrl-c it). Just from looking around on the internet it seems not possible.
Unless somebody has an idea of how to get a Radeon HD69xx working in 2560x1600 (problems being required KMS support for radeon driver and high resolution for vesa driver), this might be the end of my short venture into FreeBSD (for now). It doesn't have to be super fast, I just want to do some TeX.
I'll post my Xorg and log files tonight.
Matt