From a buddy of mine that has spent a little time with the new cards. This was in response to my email asking about his impressions of them:
It just came out in mid-September. There are a couple reasons I'm not thrilled with it:
1) no 8-port multilane version (only 12)
2) the 8-port non-multilane version is a kludge, connector-wise (a row of 3 double-stacked connectors along the edge, for 6 ports, and 2 double-stacked connectors in the middle of the board, of which the first connector in the stack is a dummy)
3) They are only on the first release of the software (9.3.0, the first- ship release, didn't work, and they released 9.3.0.1). At some point they will ship a unified release for the 9550 and 9500, but that's a ways off
4) no BBU support (yet).