Tilt, some apps can detect how you are holding the pen. Painter does (which I always hated until I got a tablet)
Graphire3 has 100 pps (points per second)
Intuos2 has 200 pps
yeah, the Intuos2 6x8 is $100 more than the Graphire3, but you will also be able to by other pens like the air brush and others. Also the Intous has a better warranty. I would consider the Graphire if I was to by a 4x5 (which is too small imho). It really depends. Some people buy a tablet and only use it once and a while, others fall in love. If you are unsure on how you are going to use it you might want to go with the Graphire3 knowing you might upgrade to the Intuos.