Grease is insanely difficult to get out. Go to the store and look in the cleaner isle. You may be able to find a cleaner that can remove some of the appearance of it, but you have a 99% chance of never fully getting the stain out.
It's not huge. Deffinatly not enough to throw it away over. It's about 3 spots, each less than the size of a penny at the bottom of the jacket. Just anoys me as the jacket is only a season old. But seeing as it's at the bottom of the jacket it's not like it needs to stay real waterproof there so I can use slightly harsher cleaning products on it.
I used to do a LOT of snowmobiling, and getting oil and grease on my gear was a constant(my newest sled was a '79 Polaris). I found that Lest Oil worked great to clean my gear. Not sure how well it will work on down filled gear, but it got almost all the oil stains out of my gear. Good luck.