Hi,
My understanding is that all behind question mark is considered by Google as not so friendly.
SEF Urls were made for human (people) not for robots or search engines - robots or search engines would probable like ?category=1 than /CategoryName (the integer than string)
In fact, no one except some of few people can say what Google likes or not but I see very unlikely that there is some specific rules for GET parameters. Even Google itself is using them normally like most of interent websites
google.com/search?hl=en&q=Phoca+Gallery&ei=-cYaVdqQNMHBUtfkgOAC&gws_rd=cr
Jan