Just enough to be unique and push the bounderies of the platform. HL2:EP1 for instance.
Erm, I wouldn't exactly describe EP1 as pushing the boundaries of the platform. In addition, EP2, TF2 and Portal are also coming out for the 360 and PS3.
But let's look at all the high profile upcoming shooters:
Crysis: PC-only (for now)
STALKER: PC-only
Bioshock: PC, 360
Quake Wars: PC, 360, PS3
Frontlines: PC, 360, PS3
ShadowRun: PC, 360
Next Wolfenstein game: 360
Now let's look at all the formerly PC-exclusive shooters that have gone console:
Battlefield (Modern Combat, Bad Company)
Ghost Recon (2, GRAW, GRAW2)
Rainbow Six (Lockdown, Vegas)
Call of Duty (2,3)
What's really sad is that there are now more console exclusive shooters than PC exclusive shooters.
The unfortunate truth of the matter is that most FPS games are being cross-developed for the consoles or designed in such a way that porting them is easy. Will we ever see a PC-exclusive shooter that truly pushes the boundaries of the genre again, like Tribes did? Highly unlikely.