The clutch problem is called "judder", and you can look at a bulletin here:http://members.cox.net/craig.hunter/03-51-02R.pdf
Basically, it makes it impossible to smoothly engage the clutch, and the whole car will shake/jerk. It gets worse in cold or damp weather. The clutch plate gets chewed up, and leaves hotspots on the flywheel.
The fix, if the car is still under warranty, is a new clutch and flywheel with the post-2003 parts (the problem will eventually return if the repair was done with pre-2003 parts).
p.s. you can visit the Subaru Crew forums on edmunds.com for more Subaru info/experiences from owners