Valve realised the mistake they made with item sets, because you had to have a hat for it to work, so they removed all the item set bonuses and replaced them with calling cards so they are still comsmetic.

but now there is no special effects for sets.......

That is kinda awesome!

Calling card aka a tombstone that drops on enemies death from your set... Maybe I don't understand the great sex appeal to this

i still have no idea what it does

thats cool

so big.