the way i see it:
from older to newer gen.
gts 450 -replaced by- gtx 550ti
gtx 460 192bit -replaced by- gtx 560se
gtx 460 256bit -replaced by- gtx 560
550ti and 560se are lower binned gpus nvidia is clearing house (making even more money from) to make room for new 600 series cards.
just like 550ti, this might not be worth the money.... some impressionable buyer might buy 560se thinking he's/she's buying a flagship card.