I just entered my pumpkin cheesecake variation into Fitday and got some interesting results. I entered it once using full-fat Philly cheese and sour cream, and once using low-fat Philly (Neufchatel) cheese and low-fat sour cream. Here are the scores for one slice (1/12 of cake):

Full Fat:
175 calories
16 grams fat
4 grams ECC (1 gram fiber from the pumpkin deducted)
4 grams protein

Lower Fat:
167 calories
14 grams fat
5 grams ECC (1 gram fiber from the pumpkin deducted)
6 grams protein

All in all, it looks like it doesn't much matter whether you use full fat or lower fat ingredients. I don't think I'll go out of my way to use the low-fat products, especially if there's anything artificial about them.

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Next I want to try a Coconut Mounds version. I'll use coconut extract, some unsweetened coconut in the batter, and SF coconut syrup as the sweetened. Then, when serving, I'll add a drizzle of SF chocolate syrup! Maybe even sprinkle a little coconut on the top as well.