You'll have to wait a while for confirmation I think as it's still not that easy to get mhl adapters or cables. Many review sites weren't even able to test it on the SII.
Hopefully someone can hack up a nice HDMI mirroring mod that supports landscape mode. The Atrix mod only supports Portrait mode and apparently it's a ton of work to get landscape working properly.
What a shame because I bought a Wiimote and Classic Wii controller specifically to use PSX and N64 emu's on my TV. It was such a pain to find that no mods/devs could get working Landscape mirroring.