I've never had the slightest hint of an issue with the oil light or any other adverse indictions, and I've been using the Fram Ultra XG6607 exclusively on my smart and my friend's smart for many, many oil changes.
If Fram offered the Ultra in the 9715 (which includes the correct relief valve pressure spec for Subaru applications), I'd use it on my wife's Forester and my Saab 9-2x (WRX clone) as well. I have absolute confidence in the Ultras, and the price at my local Walmart where I also purchase all of my oil is extremely reasonable for such a high-end filter.
As salv stated, the Ultra (at least when purchased where it's available for $8-$9 dollars) is the best off-the-shelf filter you can get for the money.