In our game with the most experienced players, 5/5. In our game with mostly experienced players who don't play often, haven't leveled up recently, and don't seem to like retraining 4/5 with the last one being a leader class who spent her feat on boosting her ability to defend her allies. In our game of almost all newbies, only 2/5. But I'm going to step in and kind of lampshade this feat when they hit level 6, because they deserve to know about it and the character builder doesn't exactly highlight its presence. Its easy for a new player without a lot of rules knowledge to miss, because they're going to focus on the recommended, race, and class feats at the top of the page, instead of on the drop down menus at the bottom.
Editted to add: the first game with 5/5 is at level 11. The second game with 4/5 is at level 5. The third game with 2/5 is at level 4. I'm permitting Expertise to cover all of your "usual" attacks rather than just attacks with a single weapon. By "usual" I mean that if your character's shtick is fighting with, say, one sword and one ax in a dual wield, then I'm going to permit you to apply one Expertise feat to both weapons.