Spartan-3 Serial LVDS max speed?

The Xilinx App Note, xapp224, suggests that it's possible to do
non-source-synchronous data recovery in a spartan-3 at up to 320 Mbps
(320 MHz) -- has anyone ever managed to get this or higher serial
speeds working in a spartan-3 PQ208 package? I'm trying to make this
work with a 100-ohm differential LVDS link and I can't seem to get my
design up past 150 Mbps.  I'm totally willing to entertain the idea
that I've got signal integrity problems, controlled impedance problems,
etc. but I'm worried that the lead inductance on the PQ208 package
might make this sort of IO impossible. 

Thanks, 
   ...Eric