[dba-Tech] Seagare Momentus XT SSHD

Does anyone have any experience with these? It's what the company calls a
Solid State Hybrid Drive -- 500GB for $80 here in Toronto. I suppose that
the "hybrid" part means that some smaller amount of the total is SSD and
the remainder traditional spinning disk. Any idea of the performance gain?
I would guess that the optimal layout would be to place the OS (and maybe
SQL Server, if there's room) on the SSD part and use the rest for normal
storage. The ad says "SSD-like performance without sacrificing capacity and
affordability" By comparison, at the same store, there's a 256GB SSD with
data transfer kit for $209.

Any informed experience, folks?
Arthur