Hi Friend,
There is no issues if you connect you users directly to blades on cat6k switch but if you think of scalability is future the number of users can increase and then it will be a costly affair to but more line cards.
Also the better design will be to have a collapse core in which you can have distribution and core on cat6k and can have edge switches for users so that if users waan a talk to some other users on same vlan they need not uses the backplane capacity of cat6k and edge switches can handle that but if they want to talk to some other users in other vlan then only the request will be send to the cat6k core switch.
So it all depends on you requirmenet and number of users but still the better design will be to have users on seperate switches conneted to core via uplink.
HTH, if yes please rate the post.
Ankur