I've had great free transfers in previous games (such as Ribery and Gourcuff), but I've only really played as Brisbane in FM11 and my best free transfers have taken on a different meaning....such as Australian, key players, on wages less than 2,000 pounds per week, and if forced to sell... for a lot of money for the club.
On the whole in FM games, I try to stay clear off marquee off-contract signings, because I like to keep my wage budget quite low...but sometimes it's hard to resist.